--刪除主鍵約束
DECLARE @Constraint_Name varchar (200)
select @Constraint_Name = Name from dbo.sysobjects

where Xtype = ‘PK‘ and Parent_Obj =

(select [ID] from dbo.sysobjects

where id = object_id(N‘[表名稱]‘)

and OBJECTPROPERTY(id, N‘IsUserTable‘) = 1)
if @Constraint_Name <> ‘‘
begin
alter table 表名稱 drop constraint @Constraint_Name
end
--刪除主鍵字段
-- 何問起 hovertree.com

declare @count int

select @count = count(*) from sysobjects a,syscolumns b

where a.id = b.id and b.name = ‘主鍵字段名‘ and a.Name = ‘表名稱‘
if @count > 0
begin
alter table 表名稱 drop column 主鍵字段名
end

--創建字段，主鍵，並自增
alter table 表名稱 add 主鍵字段名 int identity(1,1) PRIMARY KEY

SQL更改表字段為自增標識