SQLServer中的Scanf和Printf

SQLServer中有两个扩展存储过程实现Scanf和Printf功能，恰当的使用它们可以在提取和拼接字符串时大幅度简化SQL代码。

1、xp_sscanf，用它可以分解格式相对固定的字符串，这对于厌倦使用一堆substring和charindex的朋友来说不错。比如前几天的一个帖子中提出的如何分解ip地址，相对简练且通用的代码应该是下面这样

---

if (object_id ('f_getip' ) is not null )
drop function f_getip
go
create function dbo . f_getip (@ ip varchar (100 ))
returns @ t table (a int , b int , c int , d int )
as
begin
set @ ip = replace (@ ip , '.' , ' ' )
declare
@ s1 varchar (3 ) , @ s2 varchar (3 ),
@ s3 varchar (3 ) , @ s4 varchar (3 )
exec xp_sscanf @ ip , '%s %s %s %s' , @ s1 output , @ s2 output , @ s3 output , @ s4 output
insert into @ t select @ s1 , @ s2 , @ s3 , @ s4
return
end
go
select * from dbo . f_getip ('192.168.0.1' )
go
/*
a b c d
----------- ----------- ----------- -----------
192 168 0 1
*/

2、xp_sprintf，用它可以拼接出一个字符串而不用担心过多的加号很引号难以控制，比如一个动态执行sql语句的存储过程

if (object_id ('p_select' ) is not null )
drop proc p_select
go
create proc p_select (@ tb varchar (100 ), @ cols varchar (100 ), @ wherecol varchar (100 ), @ value varchar (100 ))
as
begin
declare @ s varchar (8000 )
exec xp_sprintf @ s output , 'select %s from %s where %s=''%s''' , @ cols , @ tb , @ wherecol , @ value
exec (@ s)
end
go

exec p_select 'sysobjects' , 'id,xtype,crdate' , 'name' , 'p_select'

/*

id xtype crdate
----------- ----- -----------------------
898102240 P 2009-08-18 03:01:51.153
*/