根据两个字段查找重复记录

Question

我试图修改此问题中接受的答案：Find duplicate records in MySQL，以便根据两个字段Firstname和Lastname在我的表中查找重复记录。

这是正常工作，并认为基于姓氏重复记录的原始查询...

SELECT Firstname, candidate.Lastname FROM candidate 
INNER JOIN (SELECT Lastname FROM candidate 
GROUP BY Lastname HAVING count(UserID) > 1) dup ON 
candidate.Lastname = dup.Lastname ORDER BY Lastname 

现在我想添加名字在那里，以及...但我真的不知道是什么我做的，下面不工作：

SELECT candidate.Firstname, candidate.Lastname FROM candidate 
INNER JOIN (SELECT Firstname AND Lastname FROM candidate 
GROUP BY Lastname HAVING count(UserID) > 1) dup ON 
candidate.Lastname = dup.Lastname AND candidate.Firstname = dup.Firstname 
ORDER BY Lastname 

Answer 1

看起来你只是得到了语法子查询有点不对劲，也许这就是你想要什么？

SELECT candidate.Firstname, candidate.Lastname 
FROM candidate 
INNER JOIN (
    SELECT Firstname, Lastname 
    FROM candidate 
    GROUP BY Firstname, Lastname 
    HAVING COUNT(UserID) > 1 
    ) dup 
    ON candidate.Lastname = dup.Lastname AND candidate.Firstname = dup.Firstname 
ORDER BY Lastname