【MSSQL】SqlServer中delete语句表别名的问题

1、一般情况下删除表数据的sql语句：

delete from products
where rowid>2

2、如果想给表起个别名再删除呢，就得像下面这样写了

delete products from products as p
where p.rowid>2

也可这样

delete p from products as p
where p.rowid>6

3、想一下，什么情况下删除一个表数据的时候要用别名呢？

　　之所以要用别名，是因为delete的where条件中需要用到子查询写一些条件，举例：
　　利用自连接删除表中重复的数据：

CREATE TABLE [dbo].[products1]
(
    [rowid] [int] primary key IDENTITY(1,1) NOT NULL,
    [name] [nchar](10) NULL,
    [price] [int] NULL
)

INSERT INTO Products VALUES('苹果',    50);
INSERT INTO Products VALUES('橘子',    100);
INSERT INTO Products VALUES('橘子',    100);
INSERT INTO Products VALUES('橘子',    100);
INSERT INTO Products VALUES('香蕉',    80);
INSERT INTO Products VALUES('香蕉',    80);

delete products from products as p1
where p1.rowid<
(
    select MAX(p2.rowid) from products p2
    where p1.name=p2.name and p1.price=p2.price
)
--结果：
--    rowid        name    price
--      1            苹果        50
--      4            橘子        100
--      6            香蕉        80 

4、其他数据库的情况

　　ORACLE 可以直接起别名   　

delete from products p
where p.rowid>2

　　SQLSERVER/MYSQL 可以这样起别名

delete products from products as p
where p.rowid>2

delete p from products as p
where p.rowid>6