我有一个问题，我的朋友说我必须使用表映射...但是我不知道什么是表映射，也不知道我要做什么，是否正确
我有这张桌子：员工
+-------+------------+------+-------------------------+
| ac_no | department | rank | email |
+-------+------------+------+-------------------------+
| 12ac | 01 | 08 | [email protected] |
| 1an4 | 02 | 08 | [email protected] |
| dr17 | 01 | 08 | [email protected] |
| 13IN | 01 | 05 | [email protected] |
| TE12 | 02 | 05 | [email protected] |
| GR45 | 01 | 05 | [email protected] |
+-------+------------+------+-------------------------+
我必须从表employee的数据插入表映射
目标是获取所有排名为08的数据
+-------+------------+------+-------------------------+
| 12ac | 01 | 08 | [email protected] |
| 1an4 | 02 | 08 | [email protected] |
| dr17 | 01 | 08 | [email protected] |
+-------+------------+------+-------------------------+
并查找在同一部门中排名为05的数据，然后获取电子邮件。
+-------+---------------+------------+------------------------------+
| ac_no |email | department | email |
+-------+---------------+------------+------------------------------+
| 12ac | [email protected] | 01 | [email protected];[email protected] |
| 1an4 | [email protected] | 02 | [email protected] |
| dr17 | [email protected] | 01 | [email protected];[email protected] |
+-------+---------------+------------+------------------------------+
我想使用过程将数据从表employee转换为表映射，但是我不知道该如何获取。我在工作台上制作了一个过程并运行它，以将数据插入表映射。
select ac_no,department,rank,email,(select department,email from employee where rank=05)head from employee where rank=08;
但是，如果我运行此查询，结果为
subquery returns more than 1 row抱歉，如果我问基本问题，但我真的不知道该怎么做。
最佳答案
这样尝试
select ac_no,department,rank,email from employee where rank = 08 and where department = all(select department from employee group by department)