docs/sql-manual/sql-functions/aggregate-functions/collect-set.md

{ “title”: “COLLECT_SET”, “language”: “en” }

COLLECT_SET

description

Syntax

ARRAY<T> collect_set(expr[,max_size])

Creates an array containing distinct elements from expr,with the optional max_size parameter limits the size of the resulting array to max_size elements. It has an alias group_uniq_array.

example

mysql> select k1,k2,k3 from collect_set_test order by k1;
+------+------------+-------+
| k1   | k2         | k3    |
+------+------------+-------+
|    1 | 2023-01-01 | hello |
|    2 | 2023-01-01 | NULL  |
|    2 | 2023-01-02 | hello |
|    3 | NULL       | world |
|    3 | 2023-01-02 | hello |
|    4 | 2023-01-02 | doris |
|    4 | 2023-01-03 | sql   |
+------+------------+-------+

mysql> select collect_set(k1),collect_set(k1,2) from collect_set_test;
+-------------------------+--------------------------+
| collect_set(`k1`)       | collect_set(`k1`,2)      |
+-------------------------+--------------------------+
| [4,3,2,1]               | [1,2]                    |
+----------------------------------------------------+

mysql> select k1,collect_set(k2),collect_set(k3,1) from collect_set_test group by k1 order by k1;
+------+-------------------------+--------------------------+
| k1   | collect_set(`k2`)       | collect_set(`k3`,1)      |
+------+-------------------------+--------------------------+
|    1 | [2023-01-01]            | [hello]                  |
|    2 | [2023-01-01,2023-01-02] | [hello]                  |
|    3 | [2023-01-02]            | [world]                  |
|    4 | [2023-01-02,2023-01-03] | [sql]                    |
+------+-------------------------+--------------------------+

keywords

COLLECT_SET,GROUP_UNIQ_ARRAY,COLLECT_LIST,ARRAY