我想在MySQL数据库中取出重复的记录。这可以用:

SELECT address, count(id) as cnt FROM list
GROUP BY address HAVING cnt > 1

结果是:

100 MAIN ST    2

我想要拖动它,以便它显示复制的每一行。喜欢的东西:

JIM    JONES    100 MAIN ST
JOHN   SMITH    100 MAIN ST

有什么想法可以做到吗?我试图避免做第一个,然后在代码中用第二个查询查找重复。


当前回答

 SELECT firstname, lastname, address FROM list
 WHERE 
 Address in 
 (SELECT address FROM list
 GROUP BY address
 HAVING count(*) > 1)

其他回答

会是这样的:

SELECT  t1.firstname t1.lastname t1.address FROM list  t1
    INNER JOIN  list t2 
    WHERE 
        t1.id < t2.id AND 
        t1.address = t2.address;

关键是重写这个查询,以便它可以用作子查询。

SELECT firstname, 
   lastname, 
   list.address 
FROM list
   INNER JOIN (SELECT address
               FROM   list
               GROUP  BY address
               HAVING COUNT(id) > 1) dup
           ON list.address = dup.address;
    SELECT *
    FROM (SELECT  address, COUNT(id) AS cnt
    FROM list
    GROUP BY address
    HAVING ( COUNT(id) > 1 ))

Powerlord的答案确实是最好的,我建议再做一个改变:使用LIMIT来确保db不会超载:

SELECT firstname, lastname, list.address FROM list
INNER JOIN (SELECT address FROM list
GROUP BY address HAVING count(id) > 1) dup ON list.address = dup.address
LIMIT 10

如果没有WHERE和when连接,使用LIMIT是一个好习惯。从小值开始,检查查询有多重,然后增加限制。

我们也可以发现重复依赖于不止一个字段。对于这些情况,您可以使用下面的格式。

SELECT COUNT(*), column1, column2 
FROM tablename
GROUP BY column1, column2
HAVING COUNT(*)>1;