如何修改表的ID主键 使的在删除了一些记录后把新增的记录插入到删除记录的位置

create table tab(id int identity,col varchar(20))

insert tab select '123'

union all select 'asdf'

union all select '8866'

union all select 'dfo'

union all select 'dwoie'

union all select 'fow'

go

delete tab where id=5

select * from tab

go

set identity_insert tab on

insert tab(id,col) select 5,'dfa'

set identity_insert tab off

go

select * from tab

证明一切................但是在一个数据库中只能同时只能设置一个set identity_insert 表 on