COLLECT_SET
description
Syntax
ARRAY<T> collect_set(expr)
返回一个包含 expr 中所有去重后元素(不包括NULL)的数组，数组中元素顺序是不确定的。
notice
仅支持向量化引擎中使用example
mysql> set enable_vectorized_engine=true;
mysql> select k1,k2,k3 from collect_test order by k1;
+------+------------+-------+
| k1 | k2 | k3 |
+------+------------+-------+
| 1 | 2022-07-05 | hello |
| 2 | 2022-07-04 | NULL |
| 2 | 2022-07-04 | hello |
| 3 | NULL | world |
| 3 | NULL | world |
+------+------------+-------+
mysql> select k1,collect_set(k2),collect_set(k3) from collect_test group by k1 order by k1;
+------+-------------------+-------------------+
| k1 | collect_set(`k2`) | collect_set(`k3`) |
+------+-------------------+-------------------+
| 1 | [2022-07-05] | [hello] |
| 2 | [2022-07-04] | [hello] |
| 3 | NULL | [world] |
+------+-------------------+-------------------+
keywords
COLLECT_SET,COLLECT_LIST,ARRAY