查询某表的所有字段select name from syscolumns where id = object_id(N'[dbo].[表名]') and OBJECTPROPERTY(id, N'IsUserTable') = 1查询某表是否包含某字段if  exists (Select * from syscolumns Where Name='[字段名]' And ID=OBJECT_ID('[表名]')) print '有这个字段'在现有的表中增加字段：Sql="alter table [表名] add [字段名] varchar(200)"修改字段类型：Sql="alter table [表名] Alter COLUMN 字段名]   varchar(50)"删除表：Sql="Drop table [表名]"删除字段：sql="alter table [表名] drop [字段名]"修改字段：Alter TABLE [表名] Alter COLUMN [字段名] 类型(大小) NULL新建约束：Alter TABLE [表名] ADD CONSTRAINT 约束名 CHECK ([约束字段] <= '2007-1-1')删除约束：Alter TABLE [表名] Drop CONSTRAINT 约束名新建默认值：Alter TABLE [表名] ADD CONSTRAINT 默认值名 DEFAULT 'Gziu.CoM' FOR [字段名]删除默认值：Alter TABLE [表名] Drop CONSTRAINT 默认值名