COLLECT_LIST

描述

聚合函数，用于将某一列的所有值聚集成一个数组

别名

GROUP_ARRAY

语法

COLLECT_LIST(<expr> [,<max_size>])

参数

参数	说明
`<expr>`	要聚合的列或表达式
`<max_size>`	可选参数，通过设置该参数能够将结果数组的大小限制为 max_size 个元素

返回值

返回类型是 ARRAY，该数组包含所有值。特殊情况：

如果值为 NULL，则会过滤

举例

select k1,k2,k3 from collect_list_test order by k1;

+------+------------+-------+
| k1   | k2         | k3    |
+------+------------+-------+
|    1 | 2023-01-01 | hello |
|    2 | 2023-01-02 | NULL  |
|    2 | 2023-01-02 | hello |
|    3 | NULL       | world |
|    3 | 2023-01-02 | hello |
|    4 | 2023-01-02 | sql   |
|    4 | 2023-01-03 | sql   |
+------+------------+-------+

select collect_list(k1),collect_list(k1,3) from collect_list_test;

+-------------------------+--------------------------+
| collect_list(`k1`)      | collect_list(`k1`,3)     |
+-------------------------+--------------------------+
| [1,2,2,3,3,4,4]         | [1,2,2]                  |
+-------------------------+--------------------------+

select k1,collect_list(k2),collect_list(k3,1) from collect_list_test group by k1 order by k1;

+------+-------------------------+--------------------------+
| k1   | collect_list(`k2`)      | collect_list(`k3`,1)     |
+------+-------------------------+--------------------------+
|    1 | [2023-01-01]            | [hello]                  |
|    2 | [2023-01-02,2023-01-02] | [hello]                  |
|    3 | [2023-01-02]            | [world]                  |
|    4 | [2023-01-02,2023-01-03] | [sql]                    |
+------+-------------------------+--------------------------+

BITMAP_UNION COLLECT_SET