COLLECT_LIST
description
Syntax
ARRAY<T> collect_list(expr[,max_size])
返回一个包含 expr 中所有元素(不包括NULL)的数组，可选参数max_size，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。
得到的结果数组中不包含NULL元素，数组中的元素顺序不固定。该函数具有别名group_array。
example
mysql> 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 |
+------+------------+-------+
mysql> 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] |
+-------------------------+--------------------------+
mysql> 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] |
+------+-------------------------+--------------------------+
keywords
COLLECT_LIST,GROUP_ARRAY,COLLECT_SET,ARRAY