sql如何删除表中重复的数据

Question

表 Sys_WFApproveLog_bak ,表中四个字段（logid,ver,wa,id） , 有三条记录重复，值都相同， 只有ver字段不同。 需要 删除其中的两条，只保留一条数据。如何实现，谢谢了。
logid ver wa id

7933 1 2 1
7933 2 2 1
7933 3 2 1

select LogID ,VER, *
from Sys_WFApproveLog_bak
where LogID in (select LogID from Sys_WFApproveLog_bak group by LogID having count(1) >= 2) and
logid=7933

Answer 1

过滤出全部重复
select * from a as a1 where exists(select 1 from a as a2 where a1.logid=a2.logid and a1.ver <>a2.ver )

接着删除逻辑就自己做吧，没有特别要求的话就这样

DELETE FROM A WHERE ver not in( select max(ver) from a as a1 where exists(select 1 from a as a2 where a1.logid=a2.logid and a1.ver <>a2.ver )
and
logid in ( select max(ver) from a as a1 where exists(select 1 from a as a2 where a1.logid=a2.logid and a1.ver <>a2.ver )