SQL serber 删除带有默认值的字段

declare @tableName varchar(100)='表名';declare @columnName varchar(100)='字段名';declare @constraintName varchar(200);select @constraintName=b.name from syscolumns a,sysobjects b where a.id=object_id(@tableName) and b.id=a.cdefault and a.name=@columnName and b.name like 'DF%';exec('alter table '+@tableName+' drop constraint '+@constraintName);exec ('alter table ' + @tableName + ' drop column ' + @columnName );