慎用SELECT INTO复制表

很多时候我们习惯于用SELECT INTO 复制一个表或表结构，因为它方便，快捷，而且在某些情况下效率比INSERT INTO 效率要高一些。但是要注意： SELECT INTO 复制表或表结构的时候，只是得到了一个“外壳”，就像克隆人一样，只是得到了一个躯体，个人的意识、回忆都不会克隆的。像原表的主键、外键、约束、触发器、索引都不会被复制过来。这点要注意哦，在某些情况下，没有注意的话，会照成“灾难后果的”，下面给个脚本例子，给大家演示下SELECT INTO复制表或表结构时，没有得到原表的主键、外键、约束....

准备数据Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/-->USE [MyAssistant]
GOSET ANSI_NULLS ON
GO--创建
IF OBJECT_ID(N'Groups') IS NOT NULLBEGINPRINT 'This table have been existed';DROP TABLE Groups;END 
ELSEBEGINCREATE TABLE [dbo].[Groups]([GroupID]        SMALLINT    IDENTITY(1, 1),[GroupName]      NVARCHAR(50),[Description]    NVARCHAR(100),CONSTRAINT [PK_Groups_GroupID] PRIMARY KEY(GroupID))END
GO--添加数据
INSERT INTO dbo.Groups
VALUES ('SuperAdmin', '超级管理员');INSERT INTO  dbo.Groups
VALUES('CusServGroup', '客服部门组');INSERT INTO  dbo.Groups
VALUES('CommonGroup', '普通部门组');
GODROP TABLE dbo.Users
CREATE TABLE [dbo].[Users]
([UserId]        BIGINT IDENTITY(1, 1) NOT NULL ,[UserName]      NVARCHAR(25) NULL ,[PassWord]      NVARCHAR(50) NULL ,[Sex]           BIT NULL ,[GroupID]       SMALLINT ,    CONSTRAINT [PK_Users_UserId] PRIMARY KEY CLUSTERED ( [UserId] ASC ),CONSTRAINT [FK_Users_Groups_GroupID] FOREIGN KEY(GroupID) REFERENCES Groups(GroupID)
)
GOALTER TABLE [dbo].[Users] ADD CONSTRAINT [DF_Users_Sex]  DEFAULT ((0)) FOR [Sex]
GOCREATE TRIGGER TRG_Users ON dbo.Users
AFTER DELETE
AS
SET IDENTITY_INSERT dbo.Users ON;INSERT INTO UserHistory
(UserId, UserName, PassWord, Sex, GroupID)
SELECT * FROM deleted
GOINSERT  INTO dbo.Users( UserName, PassWord, Sex, GroupID )
VALUES  ( 'Kerry', '312ddfjdf',  1,    1          )INSERT  INTO dbo.Users( UserName, PassWord, Sex, GroupID )
VALUES  ( 'test',  '312ddfjdf', 0, 3   )

我们用下面的语句复制下表Users,我们具体可以从下图中看到表User与TestUser结构的不同了