SQL SERVER可重复执行建表、建字段语句

/*
问题：type in (N'U') 中的N和U是什么意思？

答案：N是指Unicode编码，防止乱码；U是指用户表
*/
IF NOT EXISTS (SELECT * FROM sys.objects WHERE
object_id = OBJECT_ID(N'[dbo].[EVADELSECURITYPROJECT]') AND type in (N'U'))
BEGIN
CREATE TABLE EVADELSECURITYPROJECT
(
OID nvarchar(40) PRIMARY KEY,
DEALSECURITYID nvarchar(40) not null,
PROJECTID nvarchar(40) not null,
LASTUPDATETIME nvarchar(23)
)
END
else
BEGIN
print '系统中已存在EVADELSECURITYPROJECT，请检查！'
END
--判断表中列是否存在，不存在添加
IF NOT EXISTS (select * from sys.columns where object_id=OBJECT_ID(N'[dbo].[EVAASSPROJECT]') and name='CREATEUSERID')
BEGIN
alter table EVAASSPROJECT add CREATEUSERID NVARCHAR(40)
END
else
BEGIN
print 'EVAASSPROJECT表中已存在CREATEUSERID列，请检查!'
END