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