【MSSQL】SqlServer中delete語句表別名的問題

1、一般情況下刪除表數據的sql語句：

delete from products
where rowid>2

2、如果想給表起個別名再刪除呢，就得像下面這樣寫了

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

也可這樣

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

3、想一下，什么情況下刪除一個表數據的時候要用別名呢？

　　之所以要用別名，是因為delete的where條件中需要用到子查詢寫一些條件，舉例：
　　利用自連接刪除表中重復的數據：

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

INSERT INTO Products VALUES('蘋果',    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
)
--結果：
--    rowid        name    price
--      1            蘋果        50
--      4            橘子        100
--      6            香蕉        80 

4、其他數據庫的情況

　　ORACLE 可以直接起別名   　

delete from products p
where p.rowid>2

 

　　SQLSERVER/MYSQL 可以這樣起別名   

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

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