--以表名bpr000t 欄位名 level1 舉例說明新增及修改預設值約束的方法步驟
--1.檢視表bpr000t的level1欄位是否有預設值約束
select a.name as 使用者表,b.name as 欄位名,d.name as 字段預設值約束
from sysobjects a
inner join syscolumns b on (a.id = b.id)
inner join syscomments c on (b.cdefault = c.id)
inner join sysobjects d on (c.id = d.id)
where a.name = 'bpr000t' and b.name = 'level1'
--2.如果有預設值約束，刪除對應的預設值約束
declare @tablename varchar(30)
declare @fieldname varchar(50)
declare @sql varchar(300)
set @tablename = 'bpr000t'
set @fieldname = 'level1'
set @sql=''
select @sql = @sql + 'alter table ['+ a.name + '] drop constraint [' + d.name + ']'
from sysobjects a
inner join syscolumns b on (a.id = b.id)
inner join syscomments c on (b.cdefault = c.id)
inner join sysobjects d on (c.id = d.id)
where a.name = @tablename and b.name = @fieldname
exec(@sql)
--3.新增預設值約束
alter table bpr000t add default ('1') for level1 with values
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