mysql >查询语句
* 查询多条不重复记录
id name
1 a
2 b
3 c
4 c
5 b
select id, name from s1 group by name
1 a
2 b
3 c
5 b
* 查询重复记录最多的记录
select keyword, count( * ) as count
from article_keyword
group by keyword
order by count desc
limit 20
* 查询重复记录和重复次数
select user_name,count(*) as count from user_table group by user_name having count>1;
* 多联查询
s1表
id name
3 a
s2表
id s1_id age
1 2 12
2 3 23
select * from `s2` where `s1_id` = (select id from `s1` where `name` = 'a');
结果
2 3 23
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