标题: 【上海校区】常用sql语句集锦 [打印本页] 作者: 不二晨 时间: 2019-3-15 16:21 标题: 【上海校区】常用sql语句集锦 检查重复记录
select count(f_uid) num, f_uid from t_crm_user
group by f_uid having count(f_uid) > 1
order by num desc
1
2
3
删除重复记录并保留id最大的一条记录
DELETE FROM t_crm_user where f_uid IN (
SELECT f_uid from (
SELECT f_uid FROM t_crm_user GROUP BY f_uid HAVING count(f_uid) > 1
) a
) AND id NOT IN (
SELECT keepId FROM (
SELECT max(id) keepId FROM t_crm_user GROUP BY f_uid HAVING count(f_uid) > 1
) b
)
1
2
3
4
5
6
7
8
9
获取分组后每组的前三条数据
Mysql
-- 效率比较慢
select a.*
from
(
select t1.*,(select count(*)+1 from 表 where 分组字段=t1.分组字段 and 排序字段<t1.排序字段) as group_id
from 表 t1
) a
where a.group_id<=3
1
2
3
4
5
6
7
8
Oracle
SELECT t.*
FROM (SELECT ROW_NUMBER() OVER(PARTITION BY 分组字段 ORDER BY 排序字段 DESC) rn,
b.*
FROM 表 b) t
WHERE t.rn <= 3 ;
---------------------
【转载，仅作分享，侵删】
作者：storm_fury
来源：CSDN
原文：https://blog.csdn.net/weixin_43215250/article/details/84336007
版权声明：本文为博主原创文章，转载请附上博文链接！
加油，感谢分享