mysql >查询语句_MySQL

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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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