改正用户定义的数据范例[MSSQL防范]

declare @typeid int
declare @tablename varchar(50)
declare @column varchar(50)

declare @sqlstr varchar(200)
declare @defaultid int

select @typeid = xusertype
?from systypes
??where name = @typename and xusertype > 256
??AND (is_member('db_owner') = 1 OR is_member('db_ddladmin') = 1 OR is_member(user_name(uid))=1)

declare mycursor cursor for
select o.name, c.name, c.cdefault
from syscolumns c, systypes t, sysusers u, sysobjects o
where c.xusertype = @typeid
?and t.xusertype = @typeid
?and o.uid = u.uid
?and c.id = o.id
? and o.type = 'u'

open mycursor
fetch next from mycursor into @tablename, @column, @defaultid
while @@fetch_status = 0
begin
? if @defaultid <> 0
? begin
??? set @sqlstr = 'alter table ' + @tablename + ' drop ' + object_name(@defaultid)
??? exec(@sqlstr)

??? set @sqlstr = 'alter table ' + @tablename + ' alter column ' + @column + ' ' + @newtype
??? exec(@sqlstr)
???
--??? set @sqlstr = 'alter table ' + @tablename + ' add contraint ' + @tablename + 'df'+@column + ' default 0'

? end
? else
? begin
??? set @sqlstr = 'alter table ' + @tablename + ' alter column ' + @column + ' ' + @newtype

??? print @sqlstr
??? exec(@sqlstr)
? end
? --if @@error <> 0
? --? continue
? fetch next from mycursor into @tablename, @column, @defaultid
end
--假如没有约束,则可以直接删除.假若有约束.先处理约束.

close mycursor
deallocate mycursor

end

GO

create procedure SP_CHANGEFIELD(@OLDTYPENAME VARCHAR(50), @NEWDTYPE VARCHAR(50))
as
begin

? exec('sp_addtype U_LOCALTYPE, ''' + @newdtype + '''')

? exec SP_rechangfieldtype @OLDTYPENAME, 'U_LOCALTYPE'

? EXEC sp_rebuildallview

? EXEC('sp_droptype ' + @OLDTYPENAME)

? EXEC('sp_addtype ' + @OLDTYPENAME + ', ''' + @newdtype + '''')

? exec SP_rechangfieldtype 'U_LOCALTYPE', @OLDTYPENAME

? EXEC sp_rebuildallview

? EXEC sp_droptype 'U_LOCALTYPE'

end
GO

--以下是示例.将U_HELLO的长度改成 30

SP_ADDTYPE U_HELLO, 'VARCHAR(10)'

GO
CREATE TABLE TESTTYPE(NAME U_HELLO)
GO

SP_CHANGEFIELD 'U_HELLO', 'VARCHAR(30)'
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