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 * FROM booking WHERE DATE(created_at) = '2022-01-11' 和代码在( 从预订中选择代码 按代码分组 have COUNT(code) > )由id DESC订购
其他回答
SELECT t.*,(select count(*) from city as tt where tt.name=t.name) as count FROM `city` as t where (select count(*) from city as tt where tt.name=t.name) > 1 order by count desc
用你的表格替换城市。 将name替换为字段名
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
)
SELECT firstname, lastname, address FROM list
WHERE
Address in
(SELECT address FROM list
GROUP BY address
HAVING count(*) > 1)
这将在一次表传递中选择重复项，没有子查询。
SELECT *
FROM (
SELECT ao.*, (@r := @r + 1) AS rn
FROM (
SELECT @_address := 'N'
) vars,
(
SELECT *
FROM
list a
ORDER BY
address, id
) ao
WHERE CASE WHEN @_address <> address THEN @r := 0 ELSE 0 END IS NOT NULL
AND (@_address := address ) IS NOT NULL
) aoo
WHERE rn > 1
这个查询实际上模拟了Oracle和SQL Server中的ROW_NUMBER()
详见我博客上的文章:
分析函数:SUM, AVG, ROW_NUMBER -在MySQL模拟。
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。
