if exists(select A.name as DefaultName,B.name as TableName from sysobjects A inner join sysobjects B on A.parent_obj = B.id where A.xtype = 'D' and B.xtype = 'U' and B.name = 'test')

--在SQLserver中判斷指定列的默認(rèn)值是否存在
alter table test drop constraint trade_default

--因?yàn)椴荒苤苯有薷哪J(rèn)值所以先刪除默認(rèn)值約束
go 
alter table test add constraint trade_default default -1 for pid with values

--重新添加新約束，并指定默認(rèn)值
go