ARRAY_SORT

Function

If no lambda function is specified, the array elements are sorted in ascending order. Otherwise, sorting is performed according to the lambda function.

Syntax

• ARRAY_SORT(arr)
• ARRAY_SORT(lambda, arr)

Parameters

• lambda: A lambda expression used to define sorting rules, whose return value should be -1, 0, or 1 (representing less than, less than or equal to, and greater than respectively).
• arr: ARRAY<T>, where T can be numeric, boolean, string, datetime, IP, etc.

Return value

• If it does not contain a lambda expression
  • Returns ARRAY<T> of the same type as the input.
  • NULL elements are placed at the beginning of the returned array.
• If it contains a lambda expression, sort according to the lambda expression and return an ARRAY<T> of the same type as the input.

Usage notes

• If it does not contain a lambda expression
  • If the input is NULL, returns NULL; if the input is an empty array [], returns an empty array.
  • ARRAY_SORT sorts in ascending order, while ARRAY_REVERSE_SORT sorts in descending order.
• If containing a lambda expression
  • The value of the lambda expression shall be -1, 0, or 1. Should a NULL value exist, it shall be explicitly stated whether the NULL value is to be placed before or after the array.

Examples

1. Basic: NULL elements are placed at the beginning of the returned array

SELECT ARRAY_SORT([2,1,3,null]);

+--------------------------+
| ARRAY_SORT([2,1,3,null]) |
+--------------------------+
| [null, 1, 2, 3]          |
+--------------------------+

2. If the input is NULL, returns NULL; if the input is an empty array [], returns an empty array.

SELECT ARRAY_SORT(NULL);

+------------------+
| ARRAY_SORT(NULL) |
+------------------+
| NULL             |
+------------------+

SELECT ARRAY_SORT([]);

+----------------+
| ARRAY_SORT([]) |
+----------------+
| []             |
+----------------+

3. Use lambda expressions

SELECT array_sort((x, y) -> IF(x < y, 1, IF(x = y, 0, -1)), [3, 2, 5, 1, 2]);

+-----------------------------------------------------------------------+
| array_sort((x, y) -> IF(x < y, 1, IF(x = y, 0, -1)), [3, 2, 5, 1, 2]) |
+-----------------------------------------------------------------------+
| [5, 3, 2, 2, 1]                                                       |
+-----------------------------------------------------------------------+

SELECT array_sort((x, y) -> IF(x < y, 1, IF(x = y, 0, -1)), ['bc', 'ab', 'dc']);

+--------------------------------------------------------------------------+
| array_sort((x, y) -> IF(x < y, 1, IF(x = y, 0, -1)), ['bc', 'ab', 'dc']) |
+--------------------------------------------------------------------------+
| ["dc", "bc", "ab"]                                                       |
+--------------------------------------------------------------------------+

SELECT array_sort((x, y) -> CASE WHEN x IS NULL THEN -1
                              WHEN y IS NULL THEN 1
                              WHEN x < y THEN 1
                              WHEN x = y THEN 0
                              ELSE -1 END,
                              [3, 2, null, 5, null, 1, 2]);

+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| array_sort((x, y) -> CASE WHEN x IS NULL THEN -1
                              WHEN y IS NULL THEN 1
                              WHEN x < y THEN 1
                              WHEN x = y THEN 0
                              ELSE -1 END,
                              [3, 2, null, 5, null, 1, 2]) |
+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| [null, null, 5, 3, 2, 2, 1]                                                                                                                                                                                                                                                                                |
+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

SELECT array_sort((x, y) -> CASE WHEN x IS NULL THEN 1
                              WHEN y IS NULL THEN -1
                              WHEN x < y THEN 1
                              WHEN x = y THEN 0
                              ELSE -1 END,
                              [3, 2, null, 5, null, 1, 2]);

+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| array_sort((x, y) -> CASE WHEN x IS NULL THEN 1
                              WHEN y IS NULL THEN -1
                              WHEN x < y THEN 1
                              WHEN x = y THEN 0
                              ELSE -1 END,
                              [3, 2, null, 5, null, 1, 2]) |
+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| [5, 3, 2, 2, 1, null, null]                                                                                                                                                                                                                                                                                |
+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

SELECT array_sort((x, y) -> IF(length(x) < length(y), -1,
                            IF(length(x) = length(y), 0, 1)),
                            ['a', 'abcd', 'abc']);

+--------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| array_sort((x, y) -> IF(length(x) < length(y), -1,
                            IF(length(x) = length(y), 0, 1)),
                            ['a', 'abcd', 'abc']) |
+--------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| ["a", "abc", "abcd"]                                                                                                                                               |
+--------------------------------------------------------------------------------------------------------------------------------------------------------------------+

SELECT array_sort((x, y) -> IF(cardinality(x) < cardinality(y), -1,
                            IF(cardinality(x) = cardinality(y), 0, 1)),
                            [[2, 3, 1], [4, 2, 1, 4], [1, 2]]);

+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| array_sort((x, y) -> IF(cardinality(x) < cardinality(y), -1,
                            IF(cardinality(x) = cardinality(y), 0, 1)),
                            [[2, 3, 1], [4, 2, 1, 4], [1, 2]]) |
+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| [[1, 2], [2, 3, 1], [4, 2, 1, 4]]                                                                                                                                                                   |
+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+