SQLServer常用语句

• 检测某个列是否已经存在(在向表中添加一列之前执行):

  IF NOT EXISTS ( SELECT  *
              FROM    sys.columns
              WHERE   object_id = OBJECT_ID('table_name')
                      AND name = 'column_name' )
  

• 向表中添加一列并连接到另一张表的外键连接:

  ALTER TABLE [dbo].[TableA] ADD [ColumnName] [DataType] NULL
  GO
  ALTER TABLE [dbo].[TableA]  WITH CHECK ADD  CONSTRAINT [fk_TableA_ColumnName] FOREIGN KEY([ColumnName])
  REFERENCES [dbo].[TableB] ([id])
  GO
  ALTER TABLE [dbo].[TableA] CHECK CONSTRAINT [fk_TableA_ColumnName]