Question

有：表User,UserID int ,UserName varchar(20),写一个语句段或SQL语句删除表里重复的字段，要求删除后，保

持主键的唯一性

Answer 1

delete from user
where userid in (select a.id
from user a, user b
where a.name = b.name
and a.id <> b.id)

Answer 2

kk

Answer 3

delete from TABLE a where exists(select 1 from TABLE b where a.UserID=b.UserID)