如果在mysql中使用group_concat条件

Question

我有一个表有2列empid和depid.此表没有任何主键.以下是该表的数据.

+-------+-------+
| empid | depid |
+-------+-------+
|     1 |     1 |
|     1 |     2 |
|     1 |     3 |
|     1 |     4 |
|     2 |     1 |
|     2 |     2 |
|     2 |     3 |
|     2 |     4 |
+-------+-------+

现在选择我在下面查询的员工的所有depids.

select empid, group_concat(depid separator ':') from emp group by empid;

它给了我预期的输出.

+-------+-----------------------------------+
| empid | group_concat(depid separator ':') |
+-------+-----------------------------------+
|     1 | 1:2:3:4                           |
|     2 | 1:2:3:4                           |
+-------+-----------------------------------+

现在我想只选择那些大于2的depids.如何使用group_concat？

Answer 1

请尝试以下方式:

SELECT empid, GROUP_CONCAT(IF(depid > 2, depid, NULL) SEPARATOR ':') 
FROM emp
GROUP BY empid;