家都知道在sql语句中变量绑定的重大意义,甚至有高人指出:一个应用想要它变的很糟糙的话,只要不使用变量绑定就可以了。这话的确不假。这时可能有人就会问:我该绑定的都绑定了,可是我实在无法想到好的方法在in操作符中使用变量绑定。下面的方法可以解决这个疑问。
我们知道in操作符接受两种list, 一个是由一个个item组成的list,另一个是由另一个表中选出的list。第一种方式由于值个数不一定,变量绑定具有一定的困难。于是我们思路就集中到预备将一个字符串传入到sql语句中,然后使用一个方法将字符串parse成一个table, 再传回in operator:
首先我们来创建方法,及由此方法返回的table类型:
rudolf@test9i create or replace type numTableType as table
2 of number
3/
Type created.
rudolf@test9i create or replace function str2numList( p_string in varchar2 ) return
2numTableType
3as
4v_str long default p_string ',';
5v_nnumber;
6v_datanumTableType := numTableType();
7begin
8loop
9v_n := to_number(instr( v_str, ',' ));
10exit when (nvl(v_n,0) = 0);
11v_data.extend;
12v_data( v_data.count ) := ltrim(rtrim(substr(v_str,1,v_n-1)));
13v_str := substr( v_str, v_n+1 );
14end loop;
15return v_data;
16end;
17/
Function created.
我们把下列语句:
select object_name from t where object_id in ( xx,xxx,xxx,...);
改为:
select object_name from t
where object_id in
( select * fromTHE ( select cast( str2numList(:variable ) as numtableType ) fromdual )
);
现在我们来看看是否达到了我们的目的:
rudolf@test9i var STR varchar2(3000)
rudolf@test9iexec :STR := '5770,1810,4481'
PL/SQL procedure sUCcessfully completed.
rudolf@test9i alter session set events= '10046 trace name context forever, level 4'
2/
Session altered.
rudolf@test9i select object_id,object_name from t where object_id in (
2 select * fromTHE ( select cast( str2numList(:STR ) as numtableType ) from
3dual ) )
4
rudolf@test9i /
OBJECT_ID OBJECT_NAME
---------- ------------------------------
1810 ALL_ALL_TABLES
4481 AGGXMLINPUTTYPE
5770 ALL_APPLY
检查dump文件,我们看到(注重星号的行):
PARSING IN CURSOR #1 len=146 dep=0 uid=81 oct=3 lid=81 tim=1036636837633718 hv=2833917919 ad='529b9f48'
select object_id,object_name from t where object_id in (
select * fromTHE ( select cast( str2numList(:STR ) as numtableType ) from
dual ) )
END OF STMT
PARSE #1:c=0,e=655,p=0,cr=0,cu=0,mis=1,r=0,dep=0,og=0,tim=1036636837633701
BINDS #1:*****
bind 0: dty=1 mxl=2000(200) mal=00 scl=00 pre=00 oacflg=03 oacfl2=10 size=2000 offset=0
bfp=406402fc bln=2000 avl=14 flg=05
value="5770,
1810,4481"
EXEC #1:c=0,e=245,p=0,cr=0,cu=0,mis=0,r=0,dep=0,og=4,tim=1036636837645450
FETCH #1:c=20000,e=16739,p=0,cr=52,cu=0,mis=0,r=1,dep=0,og=4,tim=1036636837662283
FETCH #1:c=0,e=4644,p=0,cr=0,cu=0,mis=0,r=2,dep=0,og=4,tim=1036636837667979