Array Functions¶

array_average(array(double)) → double¶: Returns the average of all non-null elements of the array. If there are no non-null elements, returns null.

array_distinct(array(E)) -> array(E)¶

Remove duplicate values from the input array.

SELECT array_distinct(ARRAY [1, 2, 3]); -- [1, 2, 3]
SELECT array_distinct(ARRAY [1, 2, 1]); -- [1, 2]
SELECT array_distinct(ARRAY [1, NULL, NULL]); -- [1, NULL]

array_duplicates(array(E)) -> array(E)¶: Returns a set of elements that occur more than once in array. E must be bigint or varchar.

select array_duplicates(ARRAY [5, 2, 5, 1, 1, 5, null, null])); – [null, 1, 5]

array_except(array(E) x, array(E) y) -> array(E)¶

Returns an array of the elements in array x but not in array y, without duplicates.

SELECT array_except(ARRAY [1, 2, 3], ARRAY [4, 5, 6]); -- [1, 2, 3]
SELECT array_except(ARRAY [1, 2, 3], ARRAY [1, 2]); -- [3]
SELECT array_except(ARRAY [1, 2, 2], ARRAY [1, 1, 2]); -- []
SELECT array_except(ARRAY [1, 2, 2], ARRAY [1, 3, 4]); -- [2]
SELECT array_except(ARRAY [1, NULL, NULL], ARRAY [1, 1, NULL]); -- []

array_frequency(array(E) x) -> map(E, int)¶

Returns a map: keys are the unique elements in the array, values are how many times the key appears. Ignores null elements. Empty array returns empty map. E must be bigint or varchar.

SELECT array_frequency(ARRAY [1, 1, 2, 2, 2, 2]); -- {1 -> 2, 2 -> 4}
SELECT array_frequency(ARRAY [1, 1, NULL, NULL, NULL]); -- {1 -> 2}
SELECT array_frequency(ARRAY ["knock", "knock", "who", "?"]); -- {"knock" -> 2, "who" -> 1, "?" -> 1}
SELECT array_frequency(ARRAY []); -- {}

array_has_duplicates(array(E)) → boolean¶: Returns a boolean: whether array has any elements that occur more than once. E must be bigint or varchar.

select array_has_duplicates(ARRAY [5, 2, 5, 1, 1, 5, null, null])); – true

array_intersect(array(E) x, array(E) y) -> array(E)¶

Returns an array of the elements in the intersection of array x and array y, without duplicates.

SELECT array_intersect(ARRAY [1, 2, 3], ARRAY[4, 5, 6]); -- []
SELECT array_intersect(ARRAY [1, 2, 2], ARRAY[1, 1, 2]); -- [1, 2]
SELECT array_intersect(ARRAY [1, NULL, NULL], ARRAY[1, 1, NULL]); -- [1, NULL]

array_join(x, delimiter, null_replacement) → varchar¶

Concatenates the elements of the given array using the delimiter and an optional string to replace nulls.

SELECT array_join(ARRAY [1, 2, 3], ",") -- "1,2,3"
SELECT array_join(ARRAY [1, NULL, 2], ",") -- "1,2"
SELECT array_join(ARRAY [1, NULL, 2], ",", "0") -- "1,0,2"

array_max(array(E)) → E¶

Returns the maximum value of input array.

SELECT array_max(ARRAY [1, 2, 3]); -- 3
SELECT array_max(ARRAY [-1, -2, -2]); -- -1
SELECT array_max(ARRAY [-1, -2, NULL]); -- NULL
SELECT array_max(ARRAY []); -- NULL

array_min(array(E)) → E¶

Returns the minimum value of input array.

SELECT array_min(ARRAY [1, 2, 3]); -- 1
SELECT array_min(ARRAY [-1, -2, -2]); -- -2
SELECT array_min(ARRAY [-1, -2, NULL]); -- NULL
SELECT array_min(ARRAY []); -- NULL

arrays_overlap(x, y) → boolean¶: Tests if arrays x and y have any non-null elements in common. Returns null if there are no non-null elements in common but either array contains null.

array_position(x, element) → bigint¶: Returns the position of the first occurrence of the element in array x (or 0 if not found).

array_position(x, element, instance) → bigint: If instance > 0, returns the position of the instance-th occurrence of the element in array x. If instance < 0, returns the position of the instance-to-last occurrence of the element in array x. If no matching element instance is found, 0 is returned.

array_sort(array(E)) -> array(E)¶: Returns an array which has the sorted order of the input array x. The elements of x must be orderable. Null elements will be placed at the end of the returned array.

SELECT array_sort(ARRAY [1, 2, 3]); – [1, 2, 3] SELECT array_sort(ARRAY [3, 2, 1]); – [1, 2, 3] SELECT array_sort(ARRAY [2, 1, NULL]; – [1, 2, NULL] SELECT array_sort(ARRAY [NULL, 1, NULL]); – [1, NULL, NULL] SELECT array_sort(ARRAY [NULL, 2, 1]); – [1, 2, NUL]

array_sum(array(T)) → bigint/double¶: Returns the sum of all non-null elements of the array. If there is no non-null elements, returns 0. The behaviour is similar to aggregation function sum(). T must be coercible to double. Returns bigint if T is coercible to bigint. Otherwise, returns double.

cardinality(x) → bigint¶: Returns the cardinality (size) of the array x.

combinations(array(T), n) -> array(array(T))¶

Returns n- element combinations of the input array. If the input array has no duplicates, combinations returns n- element subsets. Order of subgroup is deterministic but unspecified. Order of elements within a subgroup are deterministic but unspecified. n must not be greater than 5, and the total size of subgroups generated must be smaller than 100000.

SELECT combinations(ARRAY['foo', 'bar', 'boo'],2); --[['foo', 'bar'], ['foo', 'boo']['bar', 'boo']]
SELECT combinations(ARRAY[1,2,3,4,5],3); --[[1,2,3], [1,2,4], [1,3,4], [2,3,4]]
SELECT combinations(ARRAY[1,2,2],2); --[[1,2],[1,2],[2,2]]

contains(x, element) → boolean¶: Returns true if the array x contains the element.

element_at(array(E), index) → E¶: Returns element of array at given index. If index > 0, this function provides the same functionality as the SQL-standard subscript operator ([]). If index < 0, element_at accesses elements from the last to the first.

filter(array(T), function(T, boolean)) -> array(T)¶

Constructs an array from those elements of array for which function returns true:

SELECT filter(ARRAY [], x -> true); -- []
SELECT filter(ARRAY [5, -6, NULL, 7], x -> x > 0); -- [5, 7]
SELECT filter(ARRAY [5, NULL, 7, NULL], x -> x IS NOT NULL); -- [5, 7]

reduce(array(T), initialState S, inputFunction(S, T, S), outputFunction(S, R)) → R¶

Returns a single value reduced from array. inputFunction will be invoked for each element in array in order. In addition to taking the element, inputFunction takes the current state, initially initialState, and returns the new state. outputFunction will be invoked to turn the final state into the result value. It may be the identity function (i -> i).

SELECT reduce(ARRAY [], 0, (s, x) -> s + x, s -> s); -- 0
SELECT reduce(ARRAY [5, 20, 50], 0, (s, x) -> s + x, s -> s); -- 75
SELECT reduce(ARRAY [5, 20, NULL, 50], 0, (s, x) -> s + x, s -> s); -- NULL
SELECT reduce(ARRAY [5, 20, NULL, 50], 0, (s, x) -> s + COALESCE(x, 0), s -> s); -- 75
SELECT reduce(ARRAY [5, 20, NULL, 50], 0, (s, x) -> IF(x IS NULL, s, s + x), s -> s); -- 75
SELECT reduce(ARRAY [2147483647, 1], CAST (0 AS BIGINT), (s, x) -> s + x, s -> s); -- 2147483648
SELECT reduce(ARRAY [5, 6, 10, 20], -- calculates arithmetic average: 10.25
              CAST(ROW(0.0, 0) AS ROW(sum DOUBLE, count INTEGER)),
              (s, x) -> CAST(ROW(x + s.sum, s.count + 1) AS ROW(sum DOUBLE, count INTEGER)),
              s -> IF(s.count = 0, NULL, s.sum / s.count));

repeat(element, count)¶: Repeat element for count times. count cannot be negative and must be less than or equal to 10000.

reverse(array(E)) -> array(E)¶: Returns an array which has the reversed order of the input array.

shuffle(array(E)) -> array(E)¶

Generate a random permutation of the given array:

SELECT shuffle(ARRAY [1, 2, 3]); -- [3, 1, 2] or any other random permutation
SELECT shuffle(ARRAY [0, 0, 0]); -- [0, 0, 0]
SELECT shuffle(ARRAY [1, NULL, 1, NULL, 2]); -- [2, NULL, NULL, NULL, 1] or any other random permutation

slice(array(E), start, length) -> array(E)¶: Returns a subarray starting from index start``(or starting from the end if ``start is negative) with a length of length.

subscript(array(E), index) → E¶

Returns element of array at given index. The index starts from one. Throws if the element is not present in the array. Corresponds to SQL subscript operator [].

SELECT my_array[1] AS first_element

transform(array(T), function(T, U)) -> array(U)¶

Returns an array that is the result of applying function to each element of array:

SELECT transform(ARRAY [], x -> x + 1); -- []
SELECT transform(ARRAY [5, 6], x -> x + 1); -- [6, 7]
SELECT transform(ARRAY [5, NULL, 6], x -> COALESCE(x, 0) + 1); -- [6, 1, 7]
SELECT transform(ARRAY ['x', 'abc', 'z'], x -> x || '0'); -- ['x0', 'abc0', 'z0']
SELECT transform(ARRAY [ARRAY [1, NULL, 2], ARRAY[3, NULL]], a -> filter(a, x -> x IS NOT NULL)); -- [[1, 2], [3]]

zip(array(T), array(U), ..) -> array(row(T, U, ...))¶

Returns the merge of the given arrays, element-wise into a single array of rows. The M-th element of the N-th argument will be the N-th field of the M-th output element. If the arguments have an uneven length, missing values are filled with NULL

SELECT zip(ARRAY[1, 2], ARRAY['1b', null, '3b']); -- [ROW(1, '1b'), ROW(2, null), ROW(null, '3b')]

zip_with(array(T), array(U), function(T, U, R)) -> array(R)¶

Merges the two given arrays, element-wise, into a single array using function. If one array is shorter, nulls are appended at the end to match the length of the longer array, before applying function:

SELECT zip_with(ARRAY[1, 3, 5], ARRAY['a', 'b', 'c'], (x, y) -> (y, x)); -- [ROW('a', 1), ROW('b', 3), ROW('c', 5)]
SELECT zip_with(ARRAY[1, 2], ARRAY[3, 4], (x, y) -> x + y); -- [4, 6]
SELECT zip_with(ARRAY['a', 'b', 'c'], ARRAY['d', 'e', 'f'], (x, y) -> concat(x, y)); -- ['ad', 'be', 'cf']
SELECT zip_with(ARRAY['a'], ARRAY['d', null, 'f'], (x, y) -> coalesce(x, y)); -- ['a', null, 'f']

Array Functions¶

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