檢查資料庫中是否存在某個表，不存在則生成該表
方法一：
IF NOT EXISTS (select * from dbo.sysobjects where xtype='U' and Name = 'T_Users')
BEGIN
  CREATE TABLE [dbo].[T_Users](userName varchar(20),userPass varchar(20));
END
方法二：
create procedure sel_tab
@table_name  varchar(20)
AS
  declare @flag int
  set @flag=0;
  set @flag = (select flag from (select count(*) as flag  from dbo.sysobjects where xtype='U' and Name = 'T_Users') as sel_count);
  if @flag = 0
  create table T_Users(userName varchar(20),userPass varchar(20));
GO
EXEC sel_tab "T_Users"