DECLARE @ConstraintName nvarchar(200); SELECT @ConstraintName = Name FROM SYS.DEFAULT_CONSTRAINTS WHERE PARENT_OBJECT_ID = OBJECT_ID('__TableName__') AND PARENT_COLUMN_ID = ( SELECT column_id FROM SYS.COLUMNS WHERE NAME = N'__ColumnName__' AND object_id = OBJECT_ID(N'__TableName__') ); IF @ConstraintName IS NOT NULL BEGIN EXEC('ALTER TABLE __TableName__ DROP CONSTRAINT ' + @ConstraintName); END
另外一方法(修改字段類型)sql
IF EXISTS(SELECT name FROM SYSOBJECTS WHERE name = '__TableName__' AND xtype='U') BEGIN DECLARE @name VARCHAR(100) = ( SELECT TOP 1 name FROM SYSOBJECTS WHERE name LIKE 'DF\_\_%' ESCAPE '\' AND xtype='D' AND id=(SELECT TOP 1 cdefault FROM SYSCOLUMNS WHERE id=OBJECT_ID('__TableName__') AND name='__ColumnName__') ); IF(@name IS NOT NULL) BEGIN EXEC('ALTER TABLE [DBO].[__TableName__] DROP CONSTRAINT ' + @name); EXEC('ALTER TABLE [DBO].[__TableName__] ALTER COLUMN [__ColumnName__] TEXT NULL'); END; ELSE BEGIN ALTER TABLE [DBO].[__TableName__] ALTER COLUMN [__ColumnName__] TEXT NULL; END; END;
PS:將__TableName__和__ColumnName__替換你的表名和字段名spa