遇到一个MYSQL错误

Question

要求：分组查询部门总人数

### Cause: java.sql.SQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '*)
from tb_user u
where u.department_id = ' at line 3
; bad SQL grammar []; nested exception is java.sql.SQLSyntaxErrorException:

Answer 1

Sql都写错了。用子查询就行了，不用判断是否为空，而且子查询时也不用分组，本来就是根据部门id进行查询的。

select d.id,d.name,(select count(1) from tb_user u
where u.department_id = d.id) 部门总人数 
from tb_department d