COLLECT_SET

SinceVersion 1.2.0

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.

notice

  1. Only supported in vectorized engine

example

  1. mysql> set enable_vectorized_engine=true;
  3. mysql> select k1,k2,k3 from collect_set_test order by k1;
  4. +------+------------+-------+
  5. | k1   | k2         | k3    |
  6. +------+------------+-------+
  7. |    1 | 2023-01-01 | hello |
  8. |    2 | 2023-01-01 | NULL  |
  9. |    2 | 2023-01-02 | hello |
  10. |    3 | NULL       | world |
  11. |    3 | 2023-01-02 | hello |
  12. |    4 | 2023-01-02 | doris |
  13. |    4 | 2023-01-03 | sql   |
  14. +------+------------+-------+
  16. mysql> select collect_set(k1),collect_set(k1,2) from collect_set_test;
  17. +-------------------------+--------------------------+
  18. | collect_set(`k1`)       | collect_set(`k1`,2)      |
  19. +-------------------------+--------------------------+
  20. | [4,3,2,1]               | [1,2]                    |
  21. +----------------------------------------------------+
  23. mysql> select k1,collect_set(k2),collect_set(k3,1) from collect_set_test group by k1 order by k1;
  24. +------+-------------------------+--------------------------+
  25. | k1   | collect_set(`k2`)       | collect_set(`k3`,1)      |
  26. +------+-------------------------+--------------------------+
  27. |    1 | [2023-01-01]            | [hello]                  |
  28. |    2 | [2023-01-01,2023-01-02] | [hello]                  |
  29. |    3 | [2023-01-02]            | [world]                  |
  30. |    4 | [2023-01-02,2023-01-03] | [sql]                    |
  31. +------+-------------------------+--------------------------+

keywords

COLLECT_SET,GROUP_UNIQ_ARRAY,COLLECT_LIST,ARRAY