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
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;
其他回答
不是很有效，但应该可以工作:
SELECT *
FROM list AS outer
WHERE (SELECT COUNT(*)
FROM list AS inner
WHERE inner.address = outer.address) > 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。
SELECT date FROM logs group by date having count(*) >= 2
要快速查看重复的行，可以运行一个简单的查询
在这里，我正在查询表，并列出所有重复的行相同的user_id, market_place和sku:
select user_id, market_place,sku, count(id)as totals from sku_analytics group by user_id, market_place,sku having count(id)>1;
要删除重复的行，必须决定要删除哪一行。例如id较低(通常较旧)或其他日期信息。在我的情况下，我只是想删除较低的id，因为较新的id是最新的信息。
首先仔细检查是否正确的记录将被删除。在这里，我正在选择将被删除的副本中的记录(通过唯一id)。
select a.user_id, a.market_place,a.sku from sku_analytics a inner join sku_analytics b where a.id< b.id and a.user_id= b.user_id and a.market_place= b.market_place and a.sku = b.sku;
然后我运行delete查询来删除dupes:
delete a from sku_analytics a inner join sku_analytics b where a.id< b.id and a.user_id= b.user_id and a.market_place= b.market_place and a.sku = b.sku;
备份，双重检查，验证，验证备份，然后执行。
我使用以下方法:
SELECT * FROM mytable
WHERE id IN (
SELECT id FROM mytable
GROUP BY column1, column2, column3
HAVING count(*) > 1
)
