当修改数据库的时候，如果需要修改一个not null栏位时，由于SQL SERVER自动生成的 Constraints 导致不能Alter
需要先Drop掉这个 Constraints 才可以进行。
关键问题在于 Constraints 是随机生成的，我们无法得到它的名称，不能直接drop。
该script就是用来解决这个问题的。
只要修改相应的值就好了
1
Declare @name nvarchar(128)
2Declare @tableName nvarchar(128)
3Declare @columnName nvarchar(128)
4Declare @statement nvarchar(4000)
5Set @tableName = ''
6Set @columnName = ''
7Select @name = [name] From sysobjects Left Join sysconstraints on constid = sysobjects.id
8 Where xtype = 'D' And parent_obj = object_id(@tableName)
9 And col_name(parent_obj,colid) = @columnName
10
11if @name > ''
12 begin
13 set @statement = 'Alter Table ' + @tableName + ' Drop Constraint ' + @name
14 +';Alter Table '+ @tableName + '
15 Alter Column '+ @columnName + ' char(5) NOT NULL;'
16 --Select @statement
17 exec sp_executesql @statement
18 end
19GO
20
Declare @name nvarchar(128)2
Declare @tableName nvarchar(128)3
Declare @columnName nvarchar(128)4
Declare @statement nvarchar(4000)5
Set @tableName = ''6
Set @columnName = ''7
Select @name = [name] From sysobjects Left Join sysconstraints on constid = sysobjects.id 8
Where xtype = 'D' And parent_obj = object_id(@tableName)9
And col_name(parent_obj,colid) = @columnName10
11
if @name > ''12
begin13
set @statement = 'Alter Table ' + @tableName + ' Drop Constraint ' + @name14
+';Alter Table '+ @tableName + '15
Alter Column '+ @columnName + ' char(5) NOT NULL;'16
--Select @statement17
exec sp_executesql @statement18
end 19
GO20