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]
GO

SET ANSI_NULLS ON
GO

--创建
IF OBJECT_ID(N'Groups') IS NOT NULL
    BEGIN
        PRINT 'This table have been existed';
        DROP TABLE Groups;
    END
ELSE
    BEGIN
        CREATE 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');
GO

DROP 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)
)
GO

ALTER TABLE [dbo].[Users] ADD CONSTRAINT [DF_Users_Sex]  DEFAULT ((0)) FOR [Sex]
GO

CREATE 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
GO

INSERT  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

SELECT * INTO TestUser FROM  dbo.Users