sql如何查询某字段中某字符的个数 (sql语句查询同一个字段重复的数据)

select   a.*   from   clist   a,(
  	select   cemail   from   clist   
	  group   by   cemail  
having   count(*)>1
)   as   b  
where   a.cemail=b.cemail  

查找表中多余的重复记录，重复记录是根据单个字段来判断

select * from plist
where pId in (
  	select   pid from   plist  
  	group by   pid having count
(pid) > 1)

删除表中多余的重复记录，重复记录是根据单个字段（peopleId）来判断，只留有rowid最小的记录

delete from plist
where pid in (
  	select   pid from plist 
  	group by   pid   having count
(pid) > 1)
and rowid not in (
    select min(rowid) from  plist 
		group by pid 
    having count(pid)>1)

查找表中多余的重复记录（多个字段）

select * from vlist a
where (a.pid,a.seq) in   (
  		select pid,seq from vlist 
  		group by pid,seq 
  		having  count(*) > 1)

删除表中多余的重复记录（多个字段），只留有rowid最小的记录

delete from vlist a
where (a.pid,a.seq) in   (
  		select pid,seq from vlist 
  group by pid,seq 
  having   count(*) > 1)
and rowid not in (
  	select min(rowid) from vlist 
		group by pid,seq 
		having count(*)>1)

查找表中多余的重复记录（多个字段），不包含rowid最小的记录

select * from vlist a
where (a.pid,a.seq) in   (
  		select pid,seq 
  from vlist 
  group by pid,seq 
  having  count(*) > 1)
and rowid not in (
  		select min(rowid) from   vlist 
     group by pid,seq 
     having count(*)>1)