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Array functions

array​

Introduced in: v1.1

Creates an array from the function arguments.

The arguments should be constants and have types that share a common supertype. At least one argument must be passed, because otherwise it isn't clear which type of array to create. This means that you can't use this function to create an empty array. To do so, use the emptyArray* function.

Use the [ ] operator for the same functionality.

Syntax

Arguments

  • x1 — Constant value of any type T. If only this argument is provided, the array will be of type T. - [, x2, ..., xN] — Additional N constant values sharing a common supertype with x1

Returned value

Returns an array, where 'T' is the smallest common type out of the passed arguments. Array(T)

Examples

Valid usage

Invalid usage

arrayAUCPR​

Introduced in: v20.4

Calculates the area under the precision-recall (PR) curve. A precision-recall curve is created by plotting precision on the y-axis and recall on the x-axis across all thresholds. The resulting value ranges from 0 to 1, with a higher value indicating better model performance. The PR AUC is particularly useful for imbalanced datasets, providing a clearer comparison of performance compared to ROC AUC on those cases. For more details, please see here, here and here.

Syntax

Arguments

  • cores — Scores prediction model gives. Array((U)Int*) or Array(Float*)
  • labels — Labels of samples, usually 1 for positive sample and 0 for negative sample. Array((U)Int*) or Array(Enum)
  • partial_offsets —
  • Optional. An Array(T) of three non-negative integers for calculating a partial area under the PR curve (equivalent to a vertical band of the PR space) instead of the whole AUC. This option is useful for distributed computation of the PR AUC. The array must contain the following elements [higher_partitions_tp, higher_partitions_fp, total_positives].
    • higher_partitions_tp: The number of positive labels in the higher-scored partitions.
    • higher_partitions_fp: The number of negative labels in the higher-scored partitions.
    • total_positives: The total number of positive samples in the entire dataset.
Note

When arr_partial_offsets is used, the arr_scores and arr_labels should be only a partition of the entire dataset, containing an interval of scores. The dataset should be divided into contiguous partitions, where each partition contains the subset of the data whose scores fall within a specific range. For example:

  • One partition could contain all scores in the range [0, 0.5).
  • Another partition could contain scores in the range [0.5, 1.0].

Returned value

Returns area under the precision-recall (PR) curve. Float64

Examples

Usage example

arrayAll​

Introduced in: v1.1

Returns 1 if lambda func(x [, y1, y2, ... yN]) returns true for all elements. Otherwise, it returns 0.

Syntax

Arguments

  • func(x[, y1, ..., yN]) — A lambda function which operates on elements of the source array (x) and condition arrays (y). Lambda function
  • source_arr — The source array to process. Array(T)
  • cond1_arr, ... — Optional. N condition arrays providing additional arguments to the lambda function. Array(T)

Returned value

Returns 1 if the lambda function returns true for all elements, 0 otherwise UInt8

Examples

All elements match

Not all elements match

arrayAvg​

Introduced in: v21.1

Returns the average of elements in the source array.

If a lambda function func is specified, returns the average of elements of the lambda results.

Syntax

Arguments

  • func(x[, y1, ..., yN]) — Optional. A lambda function which operates on elements of the source array (x) and condition arrays (y). Lambda function
  • source_arr — The source array to process. Array(T)
  • [, cond1_arr, ... , condN_arr] — Optional. N condition arrays providing additional arguments to the lambda function. Array(T)

Returned value

Returns the average of elements in the source array, or the average of elements of the lambda results if provided. Float64

Examples

Basic example

Usage with lambda function

arrayCompact​

Introduced in: v20.1

Removes consecutive duplicate elements from an array, including null values. The order of values in the resulting array is determined by the order in the source array.

Syntax

Arguments

  • arr — An array to remove duplicates from. Array(T)

Returned value

Returns an array without duplicate values Array(T)

Examples

Usage example

arrayConcat​

Introduced in: v1.1

Combines arrays passed as arguments.

Syntax

Arguments

  • arr1 [, arr2, ... , arrN] — N number of arrays to concatenate. Array(T)

Returned value

Returns a single combined array from the provided array arguments. Array(T)

Examples

Usage example

arrayCount​

Introduced in: v1.1

Returns the number of elements for which func(arr1[i], ..., arrN[i]) returns true. If func is not specified, it returns the number of non-zero elements in the array.

arrayCount is a higher-order function.

Syntax

Arguments

  • func — Optional. Function to apply to each element of the array(s). Lambda function
  • arr1, ..., arrN — N arrays. Array(T)

Returned value

Returns the number of elements for which func returns true. Otherwise, returns the number of non-zero elements in the array. UInt32

Examples

Usage example

arrayCumSum​

Introduced in: v1.1

Returns an array of the partial (running) sums of the elements in the source array. If a lambda function is specified, the sum is computed from applying the lambda to the array elements at each position.

Syntax

Arguments

  • func — Optional. A lambda function to apply to the array elements at each position. Lambda function
  • arr1 — The source array of numeric values. Array(T)
  • [arr2, ..., arrN] — Optional. Additional arrays of the same size, passed as arguments to the lambda function if specified. Array(T)

Returned value

Returns an array of the partial sums of the elements in the source array. The result type matches the input array's numeric type. Array(T)

Examples

Basic usage

With lambda

arrayCumSumNonNegative​

Introduced in: v18.12

Returns an array of the partial (running) sums of the elements in the source array, replacing any negative running sum with zero. If a lambda function is specified, the sum is computed from applying the lambda to the array elements at each position.

Syntax

Arguments

  • func — Optional. A lambda function to apply to the array elements at each position. Lambda function
  • arr1 — The source array of numeric values. Array(T)
  • [arr2, ..., arrN] — Optional. Additional arrays of the same size, passed as arguments to the lambda function if specified. Array(T)

Returned value

Returns an array of the partial sums of the elements in the source array, with any negative running sum replaced by zero. The result type matches the input array's numeric type. Array(T)

Examples

Basic usage

With lambda

arrayDifference​

Introduced in: v1.1

Calculates an array of differences between adjacent array elements. The first element of the result array will be 0, the second arr[1] - arr[0], the third arr[2] - arr[1], etc. The type of elements in the result array are determined by the type inference rules for subtraction (e.g. UInt8 - UInt8 = Int16).

Syntax

Arguments

  • arr — Array for which to calculate differences between adjacent elements. Array(T)

Returned value

Returns an array of differences between adjacent array elements UInt*

Examples

Usage example

Example of overflow due to result type Int64

arrayDistinct​

Introduced in: v1.1

Returns an array containing only the distinct elements of an array.

Syntax

Arguments

  • arr — Array for which to extract distinct elements. Array(T)

Returned value

Returns an array containing the distinct elements Array(T)

Examples

Usage example

arrayDotProduct​

Introduced in: v23.5

Returns the dot product of two arrays.

Note

The sizes of the two vectors must be equal. Arrays and Tuples may also contain mixed element types.

Syntax

Arguments

Returned value

The dot product of the two vectors.

Note

The return type is determined by the type of the arguments. If Arrays or Tuples contain mixed element types then the result type is the supertype.

(U)Int* or Float* or Decimal

Examples

Array example

Tuple example

arrayElement​

Introduced in: v1.1

Gets the element of the provided array with index n where n can be any integer type. If the index falls outside of the bounds of an array, it returns a default value (0 for numbers, an empty string for strings, etc.), except for arguments of a non-constant array and a constant index 0. In this case there will be an error Array indices are 1-based.

Note

Arrays in ClickHouse are one-indexed.

Negative indexes are supported. In this case, the corresponding element is selected, numbered from the end. For example, arr[-1] is the last item in the array.

Operator [n] provides the same functionality.

Syntax

Arguments

  • arr — The array to search. Array(T). - n — Position of the element to get. (U)Int*.

Returned value

Returns a single combined array from the provided array arguments Array(T)

Examples

Usage example

Negative indexing

Using [n] notation

Index out of array bounds

arrayElementOrNull​

Introduced in: v1.1

Gets the element of the provided array with index n where n can be any integer type. If the index falls outside of the bounds of an array, NULL is returned instead of a default value.

Note

Arrays in ClickHouse are one-indexed.

Negative indexes are supported. In this case, it selects the corresponding element numbered from the end. For example, arr[-1] is the last item in the array.

Syntax

Arguments

  • arrays — Arbitrary number of array arguments. Array

Returned value

Returns a single combined array from the provided array arguments. Array(T)

Examples

Usage example

Negative indexing

Index out of array bounds

arrayEnumerate​

Introduced in: v1.1

Returns the array [1, 2, 3, ..., length (arr)]

This function is normally used with the ARRAY JOIN clause. It allows counting something just once for each array after applying ARRAY JOIN. This function can also be used in higher-order functions. For example, you can use it to get array indexes for elements that match a condition.

Syntax

Arguments

  • arr — The array to enumerate. Array

Returned value

Returns the array [1, 2, 3, ..., length (arr)]. Array(UInt32)

Examples

Basic example with ARRAY JOIN

arrayEnumerateDense​

Introduced in: v18.12

Returns an array of the same size as the source array, indicating where each element first appears in the source array.

Syntax

Arguments

  • arr — The array to enumerate. Array(T)

Returned value

Returns an array of the same size as arr, indicating where each element first appears in the source array Array(T)

Examples

Usage example

arrayEnumerateDenseRanked​

Introduced in: v20.1

Returns an array the same size as the source array, indicating where each element first appears in the source array. It allows for enumeration of a multidimensional array with the ability to specify how deep to look inside the array.

Syntax

Arguments

  • clear_depth — Enumerate elements at the specified level separately. Must be less than or equal to max_arr_depth. UInt*
  • arr — N-dimensional array to enumerate. Array(T)
  • max_array_depth — The maximum effective depth. Must be less than or equal to the depth of arr. UInt*

Returned value

Returns an array denoting where each element first appears in the source array Array

Examples

Basic usage

Usage with a multidimensional array

Example with increased clear_depth

arrayEnumerateUniq​

Introduced in: v1.1

Returns an array the same size as the source array, indicating for each element what its position is among elements with the same value.

This function is useful when using ARRAY JOIN and aggregation of array elements.

The function can take multiple arrays of the same size as arguments. In this case, uniqueness is considered for tuples of elements in the same positions in all the arrays.

Syntax

Arguments

  • arr1 — First array to process. Array(T)
  • arr2, ... — Optional. Additional arrays of the same size for tuple uniqueness. Array(UInt32)

Returned value

Returns an array where each element is the position among elements with the same value or tuple. Array(T)

Examples

Basic usage

Multiple arrays

ARRAY JOIN aggregation

arrayEnumerateUniqRanked​

Introduced in: v20.1

Returns an array (or multi-dimensional array) with the same dimensions as the source array, indicating for each element what it's position is among elements with the same value. It allows for enumeration of a multi-dimensional array with the ability to specify how deep to look inside the array.

Syntax

Arguments

  • clear_depth — Enumerate elements at the specified level separately. Positive integer less than or equal to max_arr_depth. UInt*
  • arr — N-dimensional array to enumerate. Array(T)
  • max_array_depth — The maximum effective depth. Positive integer less than or equal to the depth of arr. UInt*

Returned value

Returns an N-dimensional array the same size as arr with each element showing the position of that element in relation to other elements of the same value. Array(T)

Examples

Example 1

Example 2

Example 3

Example 4

arrayExists​

Introduced in: v1.1

Returns 1 if there is at least one element in a source array for which func(x[, y1, y2, ... yN]) returns true. Otherwise, it returns 0.

Syntax

Arguments

  • func(x[, y1, ..., yN]) — A lambda function which operates on elements of the source array (x) and condition arrays (y). Lambda function
  • source_arr — The source array to process. Array(T)
  • [, cond1_arr, ... , condN_arr] — Optional. N condition arrays providing additional arguments to the lambda function. Array(T)

Returned value

Returns 1 if the lambda function returns true for at least one element, 0 otherwise UInt8

Examples

Usage example

arrayFill​

Introduced in: v20.1

The arrayFill function sequentially processes a source array from the first element to the last, evaluating a lambda condition at each position using elements from the source and condition arrays. When the lambda function evaluates to false at position i, the function replaces that element with the element at position i-1 from the current state of the array. The first element is always preserved regardless of any condition.

Syntax

Arguments

  • func(x [, y1, ..., yN]) — A lambda function func(x [, y1, y2, ... yN]) → F(x [, y1, y2, ... yN]) which operates on elements of the source array (x) and condition arrays (y). Lambda function
  • source_arr — The source array to process. Lambda function
  • [, cond1_arr, ... , condN_arr] — Optional. N condition arrays providing additional arguments to the lambda function. Array(T)

Returned value

Returns an array Array(T)

Examples

Example with single array

Example with two arrays

arrayFilter​

Introduced in: v1.1

Returns an array containing only the elements in the source array for which a lambda function returns true.

Syntax

Arguments

  • func(x[, y1, ..., yN]) — A lambda function which operates on elements of the source array (x) and condition arrays (y). Lambda function
  • source_arr — The source array to process. Array(T)
  • [, cond1_arr, ... , condN_arr] — Optional. N condition arrays providing additional arguments to the lambda function. Array(T)

Returned value

Returns a subset of the source array Array(T)

Examples

Example 1

Example 2

arrayFirst​

Introduced in: v1.1

Returns the first element in the source array for which func(x[, y1, y2, ... yN]) returns true, otherwise it returns a default value.

Syntax

Arguments

  • func(x[, y1, ..., yN]) — A lambda function which operates on elements of the source array (x) and condition arrays (y). Lambda function. - source_arr — The source array to process. Array(T). - [, cond1_arr, ... , condN_arr] — Optional. N condition arrays providing additional arguments to the lambda function. Array(T).

Returned value

Returns the first element of the source array for which λ is true, otherwise returns the default value of T.

Examples

Usage example

No match

arrayFirstIndex​

Introduced in: v1.1

Returns the index of the first element in the source array for which func(x[, y1, y2, ... yN]) returns true, otherwise it returns '0'.

Syntax

Arguments

  • func(x[, y1, ..., yN]) — A lambda function which operates on elements of the source array (x) and condition arrays (y). Lambda function. - source_arr — The source array to process. Array(T). - [, cond1_arr, ... , condN_arr] — Optional. N condition arrays providing additional arguments to the lambda function. Array(T).

Returned value

Returns the index of the first element of the source array for which func is true, otherwise returns 0 UInt32

Examples

Usage example

No match

arrayFirstOrNull​

Introduced in: v1.1

Returns the first element in the source array for which func(x[, y1, y2, ... yN]) returns true, otherwise it returns NULL.

Syntax

Arguments

  • func(x[, y1, ..., yN]) — A lambda function which operates on elements of the source array (x) and condition arrays (y). Lambda function
  • source_arr — The source array to process. Array(T)
  • [, cond1_arr, ... , condN_arr] — Optional. N condition arrays providing additional arguments to the lambda function. Array(T)

Returned value

Returns the first element of the source array for which func is true, otherwise returns NULL.

Examples

Usage example

No match

arrayFlatten​

Introduced in: v20.1

Converts an array of arrays to a flat array.

Function:

  • Applies to any depth of nested arrays.
  • Does not change arrays that are already flat.

The flattened array contains all the elements from all source arrays.

Syntax

Arguments

Returned value

Returns a flattened array from the multidimensional array Array(T)

Examples

Usage example

arrayFold​

Introduced in: v23.10

Applies a lambda function to one or more equally-sized arrays and collects the result in an accumulator.

Syntax

Arguments

  • λ(x, x1 [, x2, x3, ... xN]) — A lambda function λ(acc, x1 [, x2, x3, ... xN]) → F(acc, x1 [, x2, x3, ... xN]) where F is an operation applied to acc and array values from x with the result of acc re-used. Lambda function
  • arr1 [, arr2, arr3, ... arrN] — N arrays over which to operate. Array(T)
  • acc — Accumulator value with the same type as the return type of the Lambda function.

Returned value

Returns the final acc value.

Examples

Usage example

Fibonacci sequence

Example using multiple arrays

arrayIntersect​

Introduced in: v1.1

Takes multiple arrays and returns an array with elements which are present in all source arrays. The result contains only unique values.

Syntax

Arguments

  • arrN — N arrays from which to make the new array. Array(T).

Returned value

Returns an array with distinct elements that are present in all N arrays Array(T)

Examples

Usage example

arrayJaccardIndex​

Introduced in: v23.7

Returns the Jaccard index of two arrays.

Syntax

Arguments

Returned value

Returns the Jaccard index of arr_x and arr_y Float64

Examples

Usage example

arrayJoin​

Introduced in: v1.1

The arrayJoin function takes a row that contains an array and unfolds it, generating multiple rows – one for each element in the array. This is in contrast to Regular Functions in ClickHouse which map input values to output values within the same row, and Aggregate Functions which take a group of rows and "compress" or "reduce" them into a single summary row (or a single value within a summary row if used with GROUP BY).

All the values in the columns are simply copied, except the values in the column where this function is applied; these are replaced with the corresponding array value.

Syntax

Arguments

Returned value

Returns a set of rows unfolded from arr.

Examples

Basic usage

arrayJoin affects all sections of the query

Using multiple arrayJoin functions

Unexpected results due to optimizations

Using the ARRAY JOIN syntax

Using Tuple

arrayLast​

Introduced in: v1.1

Returns the last element in the source array for which a lambda func(x [, y1, y2, ... yN]) returns true, otherwise it returns a default value.

Syntax

Arguments

  • func(x[, y1, ..., yN]) — A lambda function which operates on elements of the source array (x) and condition arrays (y). Lambda function. - source — The source array to process. Array(T). - [, cond1, ... , condN] — Optional. N condition arrays providing additional arguments to the lambda function. Array(T).

Returned value

Returns the last element of the source array for which func is true, otherwise returns the default value of T.

Examples

Usage example

No match

arrayLastIndex​

Introduced in: v1.1

Returns the index of the last element in the source array for which func(x[, y1, y2, ... yN]) returns true, otherwise it returns '0'.

Syntax

Arguments

  • func(x[, y1, ..., yN]) — A lambda function which operates on elements of the source array (x) and condition arrays (y). Lambda function
  • source_arr — The source array to process. Array(T)
  • [, cond1_arr, ... , condN_arr] — Optional. N condition arrays providing additional arguments to the lambda function. Array(T)

Returned value

Returns the index of the last element of the source array for which func is true, otherwise returns 0 UInt32

Examples

Usage example

No match

arrayLastOrNull​

Introduced in: v1.1

Returns the last element in the source array for which a lambda func(x [, y1, y2, ... yN]) returns true, otherwise it returns NULL.

Syntax

Arguments

  • func(x [, y1, ..., yN]) — A lambda function which operates on elements of the source array (x) and condition arrays (y). Lambda function. - source_arr — The source array to process. Array(T). - [, cond1_arr, ... , condN_arr] — Optional. N condition arrays providing additional arguments to the lambda function. Array(T).

Returned value

Returns the last element of the source array for which λ is not true, otherwise returns NULL.

Examples

Usage example

No match

arrayLevenshteinDistance​

Introduced in: v25.4

Calculates the Levenshtein distance for two arrays.

Syntax

Arguments

Returned value

Levenshtein distance between the first and the second arrays. Float64

Examples

Usage example

arrayLevenshteinDistanceWeighted​

Introduced in: v25.4

Calculates Levenshtein distance for two arrays with custom weights for each element. The number of elements for the array and its weights should match.

Syntax

Arguments

Returned value

Levenshtein distance between the first and the second arrays with custom weights for each element Float64

Examples

Usage example

arrayMap​

Introduced in: v1.1

Returns an array obtained from the original arrays by applying a lambda function to each element.

Syntax

Arguments

  • func — A lambda function which operates on elements of the source array (x) and condition arrays (y). Lambda function
  • arr — N arrays to process. Array(T)

Returned value

Returns an array from the lambda results Array(T)

Examples

Usage example

Creating a tuple of elements from different arrays

arrayMax​

Introduced in: v21.1

Returns the maximum element in the source array.

If a lambda function func is specified, returns the maximum element of the lambda results.

Syntax

Arguments

  • func(x[, y1, ..., yN]) — Optional. A lambda function which operates on elements of the source array (x) and condition arrays (y). Lambda function
  • source_arr — The source array to process. Array(T)
  • [, cond1_arr, ... , condN_arr] — Optional. N condition arrays providing additional arguments to the lambda function. Array(T)

Returned value

Returns the maximum element in the source array, or the maximum element of the lambda results if provided.

Examples

Basic example

Usage with lambda function

arrayMin​

Introduced in: v21.1

Returns the minimum element in the source array.

If a lambda function func is specified, returns the minimum element of the lambda results.

Syntax

Arguments

  • func(x[, y1, ..., yN]) — Optional. A lambda function which operates on elements of the source array (x) and condition arrays (y). Lambda function
  • source_arr — The source array to process. Array(T)
  • cond1_arr, ... — Optional. N condition arrays providing additional arguments to the lambda function. Array(T)

Returned value

Returns the minimum element in the source array, or the minimum element of the lambda results if provided.

Examples

Basic example

Usage with lambda function

arrayNormalizedGini​

Introduced in: v25.1

Calculates the normalized Gini coefficient.

Syntax

Arguments

  • predicted — The predicted value. Array(T)
  • label — The actual value. Array(T)

Returned value

A tuple containing the Gini coefficients of the predicted values, the Gini coefficient of the normalized values, and the normalized Gini coefficient (= the ratio of the former two Gini coefficients) Tuple(Float64, Float64, Float64)

Examples

Usage example

arrayPartialReverseSort​

Introduced in: v23.2

This function is the same as arrayReverseSort but with an additional limit argument allowing partial sorting.

Tip

To retain only the sorted elements use arrayResize.

Syntax

Arguments

  • f(arr[, arr1, ... ,arrN]) — The lambda function to apply to elements of array x. Lambda function
  • arr — Array to be sorted. Array(T)
  • arr1, ... ,arrN — N additional arrays, in the case when f accepts multiple arguments. Array(T)
  • limit — Index value up until which sorting will occur. (U)Int*

Returned value

Returns an array of the same size as the original array where elements in the range [1..limit] are sorted in descending order. The remaining elements (limit..N] are in an unspecified order.

Examples

simple_int

simple_string

retain_sorted

lambda_simple

lambda_complex

arrayPartialShuffle​

Introduced in: v23.2

Returns an array of the same size as the original array where elements in range [1..limit] are a random subset of the original array. Remaining (limit..n] shall contain the elements not in [1..limit] range in undefined order. Value of limit shall be in range [1..n]. Values outside of that range are equivalent to performing full arrayShuffle:

Note

This function will not materialize constants.

The value of limit should be in the range [1..N]. Values outside of that range are equivalent to performing full arrayShuffle.

Syntax

Arguments

  • arr — The array to shuffle. Array(T)
  • seed — Optional. The seed to be used with random number generation. If not provided, a random one is used. (U)Int*
  • limit — Optional. The number to limit element swaps to, in the range [1..N]. (U)Int*

Returned value

Array with elements partially shuffled. Array(T)

Examples

no_limit1

no_limit2

random_seed

explicit_seed

materialize

arrayPartialSort​

Introduced in: v23.2

This function is the same as arraySort but with an additional limit argument allowing partial sorting.

Tip

To retain only the sorted elements use arrayResize.

Syntax

Arguments

  • f(arr[, arr1, ... ,arrN]) — The lambda function to apply to elements of array x. Lambda function
  • arr — Array to be sorted. Array(T)
  • arr1, ... ,arrN — N additional arrays, in the case when f accepts multiple arguments. Array(T)
  • limit — Index value up until which sorting will occur. (U)Int*

Returned value

Returns an array of the same size as the original array where elements in the range [1..limit] are sorted in ascending order. The remaining elements (limit..N] are in an unspecified order.

Examples

simple_int

simple_string

retain_sorted

lambda_simple

lambda_complex

arrayPopBack​

Introduced in: v1.1

Removes the last element from the array.

Syntax

Arguments

  • arr — The array for which to remove the last element from. Array(T)

Returned value

Returns an array identical to arr but without the last element of arr Array(T)

Examples

Usage example

arrayPopFront​

Introduced in: v1.1

Removes the first item from the array.

Syntax

Arguments

  • arr — The array for which to remove the first element from. Array(T)

Returned value

Returns an array identical to arr but without the first element of arr Array(T)

Examples

Usage example

arrayProduct​

Introduced in: v21.1

Returns the product of elements in the source array.

If a lambda function func is specified, returns the product of elements of the lambda results.

Syntax

Arguments

  • func(x[, y1, ..., yN]) — Optional. A lambda function which operates on elements of the source array (x) and condition arrays (y). Lambda function
  • source_arr — The source array to process. Array(T)
  • [, cond1_arr, ... , condN_arr] — Optional. N condition arrays providing additional arguments to the lambda function. Array(T)

Returned value

Returns the product of elements in the source array, or the product of elements of the lambda results if provided. Float64

Examples

Basic example

Usage with lambda function

arrayPushBack​

Introduced in: v1.1

Adds one item to the end of the array.

Syntax

Arguments

  • arr — The array for which to add value x to the end of. Array(T)
  • x —
  • Single value to add to the end of the array. Array(T).
Note
  • Only numbers can be added to an array with numbers, and only strings can be added to an array of strings.
  • When adding numbers, ClickHouse automatically sets the type of x for the data type of the array.
  • Can be NULL. The function adds a NULL element to an array, and the type of array elements converts to Nullable.

For more information about the types of data in ClickHouse, see Data types.

Returned value

Returns an array identical to arr but with an additional value x at the end of the array Array(T)

Examples

Usage example

arrayPushFront​

Introduced in: v1.1

Adds one element to the beginning of the array.

Syntax

Arguments

  • arr — The array for which to add value x to the end of. Array(T). - x —
  • Single value to add to the start of the array. Array(T).
Note
  • Only numbers can be added to an array with numbers, and only strings can be added to an array of strings.
  • When adding numbers, ClickHouse automatically sets the type of x for the data type of the array.
  • Can be NULL. The function adds a NULL element to an array, and the type of array elements converts to Nullable.

For more information about the types of data in ClickHouse, see Data types.

Returned value

Returns an array identical to arr but with an additional value x at the beginning of the array Array(T)

Examples

Usage example

arrayROCAUC​

Introduced in: v20.4

Calculates the area under the receiver operating characteristic (ROC) curve. A ROC curve is created by plotting True Positive Rate (TPR) on the y-axis and False Positive Rate (FPR) on the x-axis across all thresholds. The resulting value ranges from zero to one, with a higher value indicating better model performance.

The ROC AUC (also known as simply AUC) is a concept in machine learning. For more details, please see here, here and here.

Syntax

Arguments

  • scores — Scores prediction model gives. Array((U)Int*) or Array(Float*)
  • labels — Labels of samples, usually 1 for positive sample and 0 for negative sample. Array((U)Int*) or Enum
  • scale — Optional. Decides whether to return the normalized area. If false, returns the area under the TP (true positives) x FP (false positives) curve instead. Default value: true. Bool
  • partial_offsets —
  • An array of four non-negative integers for calculating a partial area under the ROC curve (equivalent to a vertical band of the ROC space) instead of the whole AUC. This option is useful for distributed computation of the ROC AUC. The array must contain the following elements [higher_partitions_tp, higher_partitions_fp, total_positives, total_negatives]. Array of non-negative Integers. Optional.
    • higher_partitions_tp: The number of positive labels in the higher-scored partitions.
    • higher_partitions_fp: The number of negative labels in the higher-scored partitions.
    • total_positives: The total number of positive samples in the entire dataset.
    • total_negatives: The total number of negative samples in the entire dataset.
Note

When arr_partial_offsets is used, the arr_scores and arr_labels should be only a partition of the entire dataset, containing an interval of scores. The dataset should be divided into contiguous partitions, where each partition contains the subset of the data whose scores fall within a specific range. For example:

  • One partition could contain all scores in the range [0, 0.5).
  • Another partition could contain scores in the range [0.5, 1.0].

Returned value

Returns area under the receiver operating characteristic (ROC) curve. Float64

Examples

Usage example

arrayRandomSample​

Introduced in: v23.10

Returns a subset with samples-many random elements of an input array. If samples exceeds the size of the input array, the sample size is limited to the size of the array, i.e. all array elements are returned but their order is not guaranteed. The function can handle both flat arrays and nested arrays.

Syntax

Arguments

  • arr — The input array or multidimensional array from which to sample elements. Array(T)
  • samples — The number of elements to include in the random sample. (U)Int*

Returned value

An array containing a random sample of elements from the input array Array(T)

Examples

Usage example

Using a multidimensional array

arrayReduce​

Introduced in: v1.1

Applies an aggregate function to array elements and returns its result. The name of the aggregation function is passed as a string in single quotes 'max', 'sum'. When using parametric aggregate functions, the parameter is indicated after the function name in parentheses 'uniqUpTo(6)'.

Syntax

Arguments

  • agg_f — The name of an aggregate function which should be a constant. String
  • arr1 [, arr2, ... , arrN)] — N arrays corresponding to the arguments of agg_f. Array(T)

Returned value

Returns the result of the aggregate function

Examples

Usage example

Example with aggregate function using multiple arguments

Example with a parametric aggregate function

arrayReduceInRanges​

Introduced in: v20.4

Applies an aggregate function to array elements in the given ranges and returns an array containing the result corresponding to each range. The function will return the same result as multiple arrayReduce(agg_func, arraySlice(arr1, index, length), ...).

Syntax

Arguments

  • agg_f — The name of the aggregate function to use. String
  • ranges — The range over which to aggregate. An array of tuples, (i, r) containing the index i from which to begin from and the range r over which to aggregate. Array(T) or Tuple(T)
  • arr1 [, arr2, ... ,arrN)] — N arrays as arguments to the aggregate function. Array(T)

Returned value

Returns an array containing results of the aggregate function over the specified ranges Array(T)

Examples

Usage example

arrayResize​

Introduced in: v1.1

Changes the length of the array.

Syntax

Arguments

  • arr — Array to resize. Array(T)
  • size — -The new length of the array. If size is less than the original size of the array, the array is truncated from the right. If size is larger than the initial size of the array, the array is extended to the right with extender values or default values for the data type of the array items.
  • extender — Value to use for extending the array. Can be NULL.

Returned value

An array of length size. Array(T)

Examples

Example 1

Example 2

arrayReverse​

Introduced in: v1.1

Reverses the order of elements of a given array.

Note

Function reverse(arr) performs the same functionality but works on other data-types in addition to Arrays.

Syntax

Arguments

  • arr — The array to reverse. Array(T)

Returned value

Returns an array of the same size as the original array containing the elements in reverse order Array(T)

Examples

Usage example

arrayReverseFill​

Introduced in: v20.1

The arrayReverseFill function sequentially processes a source array from the last element to the first, evaluating a lambda condition at each position using elements from the source and condition arrays. When the condition evaluates to false at position i, the function replaces that element with the element at position i+1 from the current state of the array. The last element is always preserved regardless of any condition.

Syntax

Arguments

  • func(x[, y1, ..., yN]) — A lambda function which operates on elements of the source array (x) and condition arrays (y). Lambda function
  • source_arr — The source array to process. Array(T)
  • [, cond1_arr, ... , condN_arr] — Optional. N condition arrays providing additional arguments to the lambda function. Array(T)

Returned value

Returns an array with elements of the source array replaced by the results of the lambda. Array(T)

Examples

Example with a single array

Example with two arrays

arrayReverseSort​

Introduced in: v1.1

Sorts the elements of an array in descending order. If a function f is specified, the provided array is sorted according to the result of the function applied to the elements of the array, and then the sorted array is reversed. If f accepts multiple arguments, the arrayReverseSort function is passed several arrays that the arguments of func will correspond to.

If the array to sort contains -Inf, NULL, NaN, or Inf they will be sorted in the following order:

  1. -Inf
  2. Inf
  3. NaN
  4. NULL

arrayReverseSort is a higher-order function.

Syntax

Arguments

  • f(y1[, y2 ... yN]) — The lambda function to apply to elements of array x. - arr — An array to be sorted. Array(T) - arr1, ..., yN — Optional. N additional arrays, in the case when f accepts multiple arguments.

Returned value

Returns the array x sorted in descending order if no lambda function is provided, otherwise it returns an array sorted according to the logic of the provided lambda function, and then reversed. Array(T).

Examples

Example 1

Example 2

arrayReverseSplit​

Introduced in: v20.1

Split a source array into multiple arrays. When func(x[, y1, ..., yN]) returns something other than zero, the array will be split to the right of the element. The array will not be split after the last element.

Syntax

Arguments

  • func(x[, y1, ..., yN]) — A lambda function which operates on elements of the source array (x) and condition arrays (y). Lambda function
  • source_arr — The source array to process. Lambda function
  • [, cond1_arr, ... , condN_arr] — Optional. N condition arrays providing additional arguments to the lambda function. Array(T)

Returned value

Returns an array of arrays. Array(Array(T))

Examples

Usage example

arrayRotateLeft​

Introduced in: v23.8

Rotates an array to the left by the specified number of elements. Negative values of n are treated as rotating to the right by the absolute value of the rotation.

Syntax

Arguments

Returned value

An array rotated to the left by the specified number of elements Array(T)

Examples

Usage example

Negative value of n

arrayRotateRight​

Introduced in: v23.8

Rotates an array to the right by the specified number of elements. Negative values of n are treated as rotating to the left by the absolute value of the rotation.

Syntax

Arguments

Returned value

An array rotated to the right by the specified number of elements Array(T)

Examples

Usage example

Negative value of n

arrayShiftLeft​

Introduced in: v23.8

Shifts an array to the left by the specified number of elements. New elements are filled with the provided argument or the default value of the array element type. If the number of elements is negative, the array is shifted to the right.

Syntax

Arguments

  • arr — The array for which to shift the elements.Array(T). - n — Number of elements to shift.(U)Int8/16/32/64. - default — Optional. Default value for new elements.

Returned value

An array shifted to the left by the specified number of elements Array(T)

Examples

Usage example

Negative value of n

Using a default value

arrayShiftRight​

Introduced in: v23.8

Shifts an array to the right by the specified number of elements. New elements are filled with the provided argument or the default value of the array element type. If the number of elements is negative, the array is shifted to the left.

Syntax

Arguments

  • arr — The array for which to shift the elements. Array(T)
  • n — Number of elements to shift. (U)Int8/16/32/64
  • default — Optional. Default value for new elements.

Returned value

An array shifted to the right by the specified number of elements Array(T)

Examples

Usage example

Negative value of n

Using a default value

arrayShingles​

Introduced in: v24.1

Generates an array of shingles (similar to ngrams for strings), i.e. consecutive sub-arrays with a specified length of the input array.

Syntax

Arguments

  • arr — Array for which to generate an array of shingles. Array(T)
  • l — The length of each shingle. (U)Int*

Returned value

An array of generated shingles Array(T)

Examples

Usage example

arrayShuffle​

Introduced in: v23.2

Returns an array of the same size as the original array containing the elements in shuffled order. Elements are reordered in such a way that each possible permutation of those elements has equal probability of appearance.

Note

This function will not materialize constants.

Syntax

Arguments

  • arr — The array to shuffle. Array(T)
  • seed (optional) — Optional. The seed to be used with random number generation. If not provided a random one is used. (U)Int*

Returned value

Array with elements shuffled Array(T)

Examples

Example without seed (unstable results)

Example without seed (stable results)

arraySimilarity​

Introduced in: v25.4

Calculates the similarity of two arrays from 0 to 1 based on weighted Levenshtein distance.

Syntax

Arguments

Returned value

Returns the similarity between 0 and 1 of the two arrays based on the weighted Levenshtein distance Float64

Examples

Usage example

arraySlice​

Introduced in: v1.1

Returns a slice of the array, with NULL elements included.

Syntax

Arguments

  • arr — Array to slice. Array(T)
  • offset — Indent from the edge of the array. A positive value indicates an offset on the left, and a negative value is an indent on the right. Numbering of the array items begins with 1. (U)Int*
  • length — The length of the required slice. If you specify a negative value, the function returns an open slice [offset, array_length - length]. If you omit the value, the function returns the slice [offset, the_end_of_array]. (U)Int*

Returned value

Returns a slice of the array with length elements from the specified offset Array(T)

Examples

Usage example

arraySort​

Introduced in: v1.1

Sorts the elements of the provided array in ascending order. If a lambda function f is specified, sorting order is determined by the result of the lambda applied to each element of the array. If the lambda accepts multiple arguments, the arraySort function is passed several arrays that the arguments of f will correspond to.

If the array to sort contains -Inf, NULL, NaN, or Inf they will be sorted in the following order:

  1. -Inf
  2. Inf
  3. NaN
  4. NULL

arraySort is a higher-order function.

Syntax

Arguments

  • f(y1[, y2 ... yN]) — The lambda function to apply to elements of array x. - arr — An array to be sorted. Array(T) - arr1, ..., yN — Optional. N additional arrays, in the case when f accepts multiple arguments.

Returned value

Returns the array arr sorted in ascending order if no lambda function is provided, otherwise it returns an array sorted according to the logic of the provided lambda function. Array(T).

Examples

Example 1

Example 2

Example 3

arraySplit​

Introduced in: v20.1

Split a source array into multiple arrays. When func(x [, y1, ..., yN]) returns something other than zero, the array will be split to the left of the element. The array will not be split before the first element.

Syntax

Arguments

  • func(x[, y1, ..., yN]) — A lambda function which operates on elements of the source array (x) and condition arrays (y).Lambda function. - source_arr — The source array to split Array(T). - [, cond1_arr, ... , condN_arr] — Optional. N condition arrays providing additional arguments to the lambda function. Array(T).

Returned value

Returns an array of arrays Array(Array(T))

Examples

Usage example

arrayStringConcat​

Introduced in: v1.1

Concatenates the elements of an array of strings into a single string, using the specified delimiter between elements.

Syntax

Arguments

  • arr — The source array of strings. Array(String)
  • delimiter — Optional.The delimiter to insert between elements. Defaults to empty string if not specified. String

Returned value

A string consisting of the array elements joined by the delimiter. String

Examples

Basic usage

With delimiter

arraySum​

Introduced in: v21.1

Returns the sum of elements in the source array.

If a lambda function func is specified, returns the sum of elements of the lambda results.

Syntax

Arguments

  • func(x[, y1, ..., yN]) — Optional. A lambda function which operates on elements of the source array (x) and condition arrays (y). Lambda function
  • source_arr — The source array to process. Array(T)
  • , cond1_arr, ... , condN_arr] — Optional. N condition arrays providing additional arguments to the lambda function. Array(T)

Returned value

Returns the sum of elements in the source array, or the sum of elements of the lambda results if provided.

Examples

Basic example

Usage with lambda function

arraySymmetricDifference​

Introduced in: v25.4

Takes multiple arrays and returns an array with elements that are not present in all source arrays. The result contains only unique values.

Note

The symmetric difference of more than two sets is mathematically defined as the set of all input elements which occur in an odd number of input sets. In contrast, function arraySymmetricDifference simply returns the set of input elements which do not occur in all input sets.

Syntax

Arguments

  • arrN — N arrays from which to make the new array. Array(T).

Returned value

Returns an array of distinct elements not present in all source arrays Array(T)

Examples

Usage example

arrayUnion​

Introduced in: v24.10

Takes multiple arrays and returns an array which contains all elements that are present in one of the source arrays.The result contains only unique values.

Syntax

Arguments

  • arrN — N arrays from which to make the new array. Array(T)

Returned value

Returns an array with distinct elements from the source arrays Array(T)

Examples

Usage example

arrayUniq​

Introduced in: v1.1

For a single argument passed, counts the number of different elements in the array. For multiple arguments passed, it counts the number of different tuples made of elements at matching positions across multiple arrays.

For example SELECT arrayUniq([1,2], [3,4], [5,6]) will form the following tuples:

  • Position 1: (1,3,5)
  • Position 2: (2,4,6)

It will then count the number of unique tuples. In this case 2.

All arrays passed must have the same length.

Tip

If you want to get a list of unique items in an array, you can use arrayReduce('groupUniqArray', arr).

Syntax

Arguments

  • arr1 — Array for which to count the number of unique elements. Array(T)
  • [, arr2, ..., arrN] — Optional. Additional arrays used to count the number of unique tuples of elements at corresponding positions in multiple arrays. Array(T)

Returned value

For a single argument returns the number of unique elements. For multiple arguments returns the number of unique tuples made from elements at corresponding positions across the arrays. UInt32

Examples

Single argument

Multiple argument

arrayWithConstant​

Introduced in: v20.1

Creates an array of length length filled with the constant x.

Syntax

Arguments

  • length — Number of elements in the array. (U)Int*
  • x — The value of the N elements in the array, of any type.

Returned value

Returns an Array with N elements of value x. Array(T)

Examples

Usage example

arrayZip​

Introduced in: v20.1

Combines multiple arrays into a single array. The resulting array contains the corresponding elements of the source arrays grouped into tuples in the listed order of arguments.

Syntax

Arguments

  • arr1, arr2, ... , arrN — N arrays to combine into a single array. Array(T)

Returned value

Returns an array with elements from the source arrays grouped in tuples. Data types in the tuple are the same as types of the input arrays and in the same order as arrays are passed Array(T)

Examples

Usage example

arrayZipUnaligned​

Introduced in: v20.1

Combines multiple arrays into a single array, allowing for unaligned arrays (arrays of differing lengths). The resulting array contains the corresponding elements of the source arrays grouped into tuples in the listed order of arguments.

Syntax

Arguments

  • arr1, arr2, ..., arrN — N arrays to combine into a single array. Array(T)

Returned value

Returns an array with elements from the source arrays grouped in tuples. Data types in the tuple are the same as types of the input arrays and in the same order as arrays are passed. Array(T) or Tuple(T1, T2, ...)

Examples

Usage example

countEqual​

Introduced in: v1.1

Returns the number of elements in the array equal to x. Equivalent to arrayCount(elem -> elem = x, arr).

NULL elements are handled as separate values.

Syntax

Arguments

  • arr — Array to search. Array(T)
  • x — Value in the array to count. Any type.

Returned value

Returns the number of elements in the array equal to x UInt64

Examples

Usage example

empty​

Introduced in: v1.1

Checks whether the input array is empty.

An array is considered empty if it does not contain any elements.

Note

Can be optimized by enabling the optimize_functions_to_subcolumns setting. With optimize_functions_to_subcolumns = 1 the function reads only size0 subcolumn instead of reading and processing the whole array column. The query SELECT empty(arr) FROM TABLE; transforms to SELECT arr.size0 = 0 FROM TABLE;.

The function also works for strings or UUID.

Syntax

Arguments

Returned value

Returns 1 for an empty array or 0 for a non-empty array UInt8

Examples

Usage example

emptyArrayDate​

Introduced in: v1.1

Returns an empty Date array

Syntax

Arguments

  • None. Returned value

An empty Date array. Array(T)

Examples

Usage example

emptyArrayDateTime​

Introduced in: v1.1

Returns an empty DateTime array

Syntax

Arguments

  • None. Returned value

An empty DateTime array. Array(T)

Examples

Usage example

emptyArrayFloat32​

Introduced in: v1.1

Returns an empty Float32 array

Syntax

Arguments

  • None. Returned value

An empty Float32 array. Array(T)

Examples

Usage example

emptyArrayFloat64​

Introduced in: v1.1

Returns an empty Float64 array

Syntax

Arguments

  • None. Returned value

An empty Float64 array. Array(T)

Examples

Usage example

emptyArrayInt16​

Introduced in: v1.1

Returns an empty Int16 array

Syntax

Arguments

  • None. Returned value

An empty Int16 array. Array(T)

Examples

Usage example

emptyArrayInt32​

Introduced in: v1.1

Returns an empty Int32 array

Syntax

Arguments

  • None. Returned value

An empty Int32 array. Array(T)

Examples

Usage example

emptyArrayInt64​

Introduced in: v1.1

Returns an empty Int64 array

Syntax

Arguments

  • None. Returned value

An empty Int64 array. Array(T)

Examples

Usage example

emptyArrayInt8​

Introduced in: v1.1

Returns an empty Int8 array

Syntax

Arguments

  • None. Returned value

An empty Int8 array. Array(T)

Examples

Usage example

emptyArrayString​

Introduced in: v1.1

Returns an empty String array

Syntax

Arguments

  • None. Returned value

An empty String array. Array(T)

Examples

Usage example

emptyArrayToSingle​

Introduced in: v1.1

Accepts an empty array and returns a one-element array that is equal to the default value.

Syntax

Arguments

Returned value

An array with a single value of the Array's default type. Array(T)

Examples

Basic example

emptyArrayUInt16​

Introduced in: v1.1

Returns an empty UInt16 array

Syntax

Arguments

  • None. Returned value

An empty UInt16 array. Array(T)

Examples

Usage example

emptyArrayUInt32​

Introduced in: v1.1

Returns an empty UInt32 array

Syntax

Arguments

  • None. Returned value

An empty UInt32 array. Array(T)

Examples

Usage example

emptyArrayUInt64​

Introduced in: v1.1

Returns an empty UInt64 array

Syntax

Arguments

  • None. Returned value

An empty UInt64 array. Array(T)

Examples

Usage example

emptyArrayUInt8​

Introduced in: v1.1

Returns an empty UInt8 array

Syntax

Arguments

  • None. Returned value

An empty UInt8 array. Array(T)

Examples

Usage example

has​

Introduced in: v1.1

Returns whether the array contains the specified element.

Syntax

Arguments

  • arr — The source array. Array(T)
  • x — The value to search for in the array.

Returned value

Returns 1 if the array contains the specified element, otherwise 0. UInt8

Examples

Basic usage

Not found

hasAll​

Introduced in: v1.1

Checks whether one array is a subset of another.

  • An empty array is a subset of any array.
  • Null is processed as a value.
  • The order of values in both the arrays does not matter.

Syntax

Arguments

  • set — Array of any type with a set of elements. Array(T)
  • subset — Array of any type that shares a common supertype with set containing elements that should be tested to be a subset of set. Array(T)

Returned value

  • 1, if set contains all of the elements from subset.
  • 0, otherwise.

Raises a NO_COMMON_TYPE exception if the set and subset elements do not share a common supertype.

Examples

Empty arrays

Arrays containing NULL values

Arrays containing values of a different type

Arrays containing String values

Arrays without a common type

Array of arrays

hasAny​

Introduced in: v1.1

Checks whether two arrays have intersection by some elements.

  • Null is processed as a value.
  • The order of the values in both of the arrays does not matter.

Syntax

Arguments

  • arr_x — Array of any type with a set of elements. Array(T)
  • arr_y — Array of any type that shares a common supertype with array arr_x. Array(T)

Returned value

  • 1, if arr_x and arr_y have one similar element at least.
  • 0, otherwise.

Raises a NO_COMMON_TYPE exception if any of the elements of the two arrays do not share a common supertype.

Examples

One array is empty

Arrays containing NULL values

Arrays containing values of a different type

Arrays without a common type

Array of arrays

hasSubstr​

Introduced in: v20.6

Checks whether all the elements of array2 appear in a array1 in the same exact order. Therefore, the function will return 1, if and only if array1 = prefix + array2 + suffix.

In other words, the functions will check whether all the elements of array2 are contained in array1 like the hasAll function. In addition, it will check that the elements are observed in the same order in both array1 and array2.

  • The function will return 1 if array2 is empty.
  • Null is processed as a value. In other words hasSubstr([1, 2, NULL, 3, 4], [2,3]) will return 0. However, hasSubstr([1, 2, NULL, 3, 4], [2,NULL,3]) will return 1
  • The order of values in both the arrays does matter.

Raises a NO_COMMON_TYPE exception if any of the elements of the two arrays do not share a common supertype.

Syntax

Arguments

  • arr1 — Array of any type with a set of elements. Array(T)
  • arr2 — Array of any type with a set of elements. Array(T)

Returned value

Returns 1 if array arr1 contains array arr2. Otherwise, returns 0. UInt8

Examples

Both arrays are empty

Arrays containing NULL values

Arrays containing values of a different type

Arrays containing strings

Arrays with valid ordering

Arrays with invalid ordering

Array of arrays

Arrays without a common type

indexOf​

Introduced in: v1.1

Returns the index of the first element with value 'x' (starting from 1) if it is in the array. If the array does not contain the searched-for value, the function returns 0.

Elements set to NULL are handled as normal values.

Syntax

Arguments

  • arr — An array to search in for x. Array(T)
  • x — Value of the first matching element in arr for which to return an index. UInt64

Returned value

Returns the index (numbered from one) of the first x in arr if it exists. Otherwise, returns 0. UInt64

Examples

Basic example

Array with nulls

indexOfAssumeSorted​

Introduced in: v24.12

Returns the index of the first element with value 'x' (starting from 1) if it is in the array. If the array does not contain the searched-for value, the function returns 0.

Note

Unlike the indexOf function, this function assumes that the array is sorted in ascending order. If the array is not sorted, results are undefined.

Syntax

Arguments

  • arr — A sorted array to search. Array(T)
  • x — Value of the first matching element in sorted arr for which to return an index. UInt64

Returned value

Returns the index (numbered from one) of the first x in arr if it exists. Otherwise, returns 0. UInt64

Examples

Basic example

length​

Introduced in: v1.1

Calculates the length of a string or array.

  • For String or FixedString arguments: calculates the number of bytes in the string.
  • For Array arguments: calculates the number of elements in the array.
  • If applied to a FixedString argument, the function is a constant expression.

Please note that the number of bytes in a string is not the same as the number of Unicode "code points" and it is not the same as the number of Unicode "grapheme clusters" (what we usually call "characters") and it is not the same as the visible string width.

It is ok to have ASCII NUL bytes in strings, and they will be counted as well.

Syntax

Arguments

  • x — Value for which to calculate the number of bytes (for String/FixedString) or elements (for Array). String or FixedString or Array(T)

Returned value

Returns the number of number of bytes in the String/FixedString x / the number of elements in array x UInt64

Examples

string1

arr1

constexpr

unicode

ascii_vs_utf8

notEmpty​

Introduced in: v1.1

Checks whether the input array is non-empty.

An array is considered non-empty if it contains at least one element.

Note

Can be optimized by enabling the optimize_functions_to_subcolumns setting. With optimize_functions_to_subcolumns = 1 the function reads only size0 subcolumn instead of reading and processing the whole array column. The query SELECT notEmpty(arr) FROM table transforms to SELECT arr.size0 != 0 FROM TABLE.

The function also works for strings or UUID.

Syntax

Arguments

Returned value

Returns 1 for a non-empty array or 0 for an empty array UInt8

Examples

Usage example

range​

Introduced in: v1.1

Returns an array of numbers from start to end - 1 by step.

The supported types are:

  • UInt8/16/32/64

  • Int8/16/32/64]

  • All arguments start, end, step must be one of the above supported types. Elements of the returned array will be a super type of the arguments.

  • An exception is thrown if the function returns an array with a total length more than the number of elements specified by setting function_range_max_elements_in_block.

  • Returns NULL if any argument has Nullable(nothing) type. An exception is thrown if any argument has NULL value (Nullable(T) type).

Syntax

Arguments

  • start — Optional. The first element of the array. Required if step is used. Default value: 0. - end — Required. The number before which the array is constructed. - step — Optional. Determines the incremental step between each element in the array. Default value: 1.

Returned value

Array of numbers from start to end - 1 by step. Array(T)

Examples

Usage example

reverse​

Introduced in: v1.1

Reverses the order of the elements in the input array or the characters in the input string.

Syntax

Arguments

Returned value

Returns an array or string with the order of elements or characters reversed.

Examples

Reverse array

Reverse string

Distance functions​

All supported functions are described in distance functions documentation.