mysql - 嵌套 JOIN 在 MySQL 中查找具有多个 WHERE 条件的记录

Question

Using this solution ，我学会了如何嵌套查询，但我发现 WHERE 语句被忽略了？

我只想返回在定量表中找到指定的 4 个 QualID 的 EmpID。看起来这会返回 EmpID，其中任何这些值都与 EmpID 匹配。

员工表: EmpID、EmpName

资格表: EmpID、QualID

SELECT EmpID, QualID
FROM
(
   SELECT Employee.EmpID as EmpID, HTG_TechQual.QualID as QualID 
   FROM Employee Employee 
   INNER JOIN Qualifications Qualifications ON Qualifications.EmpID = Employee.EmpID
   WHERE Qualifications.QualID IN ('3', '34', '35', '37')
 ) X
GROUP BY EmpID DESC

Answer 1

使用 HAVING 子句仅选择具有全部 4 个 QualID 的组

SELECT e.EmpID
FROM Employee e 
INNER JOIN Qualifications q ON q.EmpID = e.EmpID
WHERE q.QualID IN ('3', '34', '35', '37')
GROUP BY e.EmpID
HAVING count(distinct q.QualID) = 4