请教一个关于php+mysql的问题

回复讨论(解决方案)

首先你的数据当中必须有一个id,一个uid

查询uid为1,2,3分别都几条：（假定表名为'user',表中只有两个字段，分别为id和uid）

select id,count(uid) from user group by uid having uid=1 or uid=2 or uid =3;

select * from user where uid=1 limit 1;

你可以 对查询出来的结果集 在分组 取一条

select * from tbl_name a  where (select count(*) from tbl_name where uid=a.uid and id 
 
  每个条件只取一条：  
  select * from tt where uid in(1,2,3) group by uid ; 
 
  select  a.*  from  table a where  1> (select count(1) from table b where a.id = b.id and a.id > b.id ) and a.uid in (1,2,3) 
 
  select top 1 * from table group by  id  
 
  group by 可以实现