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假设:
table business
字段 name
怎样把已经有数据的表business,去掉name字段的值相同的记录呢?
蚂蚁的：去除重复值
如果有ID字段，就是具有唯一性的字段
delect table where id not in (
select max(id) from table group by col1,col2,col3...
)
group by 子句后跟的字段就是你用来判断重复的条件，如只有col1，那么只要col1字段内容相同即表示记录相同。
2,如果是判断所有字段也可以这样
select * into #aa from table group by id1,id2,....
delete table
insert into table
select * from #aa
3，没有ID的情况
select identity(int,1,1) as id,* into #temp from tabel
delect # where id not in (
select max(id) from # group by col1,col2,col3...)
delect table
inset into table(...)
select ..... from #temp
col1+,+col2+,...col5 联合主键
select * from table where col1+,+col2+,...col5 in (
select max(col1+,+col2+,...col5) from table
where having count(*)>1
group by col1,col2,col3,col4
)
group by 子句后跟的字段就是你用来判断重复的条件，如只有col1，那么只要col1字段内容相同即表示记录相同。
2,
select identity(int,1,1) as id,* into #temp from tabel
select * from #temp where id in (
select max(id) from #emp where having count(*)>1 group by col1,col2,col3...)
你的表需要有一个唯一性字段才行。
delete from tablename a where a.name in (select name from tablename b where a.name<>b.name)
有主键就好办了,设你id为主键
delete from business a
where id not in (select id from business b where id <>a.id )
如果有ID字段，就是具有唯一性的字段
delect table where id not in (
select max(id) from table group by col1,col2,col3...
)
group by 子句后跟的字段就是你用来判断重复的条件，如只有col1，那么只要col1字段内容相同即表示记录相同。
我的看法是：这种方法只能解决name只重复一次的情况，要不就是多次运行，直到没有记录重复为止。
create table #tt(name char(50))
insert into # tt (select distinct name from business)
delete from business
insert into business (select * from #tt)
drop table #tt
