Sql 如何基于纯匹配条件应用过滤器？

从下表中，我想筛选纯粹属于类别1的员工

+---------+----------+
| EMPNAME | Category |
+---------+----------+
| aaa     |        1 |
| aaa     |        2 |
| aaa     |        3 |
| bbb     |        2 |
| bbb     |        3 |
| ccc     |        1 |
| ddd     |        1 |
| ddd     |        2 |
| eee     |        1 |
| fff     |        3 |
| ggg     |        2 |
| hhh     |        1 |
| hhh     |        2 |
| hhh     |        3 |
| iii     |        2 |
| jjj     |        3 |
| kkk     |        1 |
+---------+----------+

已尝试where子句，但员工aaa也会出现错误的结果。

您可以使用group by和having count

select * from yourtable t1
where not exists
(
    select 1
    from yourtable t2
    where t1.EMPNAME=t2.EMPNAME
    and t2.Category<>1
)

除以下情况外使用：

---

这是什么？aaa 1aaa是具有类别1、2和3的员工姓名。您的预期结果是什么。实际上不需要类别=1。

select * from table1 where empname in (select empname from table1 
group by empname 
having count(category) = 1) and category = 1

SELECT EMPNAME
FROM table
WHERE Category = 1

EXCEPT

SELECT EMPNAME
FROM table
WHERE Category <> 1