Ascii 0 在資料庫上造成的困擾

select dump(BEFORECOSIGNEREMPNO) from A.test
where NURSEGIVEDRUGIDSE IN (289839402,289769909) AND BEFORECOSIGNEREMPNO IS not NULL;
-------------------------------------
Typ=96 Len=6: 0,0,0,0,10,0
Typ=96 Len=6: 80,48,48,50,55,0

create table test1
as 
select * from dual;
alter table test1
add a varchar2(1 byte);
insert into test1
select 'x',null from dual;
commit;
select dump(a) from test1;
-------------------------------------
Typ=1 Len=1: 49
NULL

--我們手動塞一個ascii 為0的值到資料庫中(ascii 0 : Null)
update test1 set a=chr(0) where dummy='x';    
commit;
select dump(a),nvl(a,'is null'),a.* from test1 a;
-------------------------------------
Typ=1 Len=1: 49    1    X    1
Typ=1 Len=1: 0            x

--我們塞一個ascii 32 來當成空白
insert into test1
select 'y',chr(32) from dual;     
--我們塞一個空白字元進去
insert into test1
select 'y',' ' from dual;              
commit;
select dump(a),length(a),a.* from test1 a where dummy='y';
-------------------------------------
Typ=1 Len=1: 32    1    y     
Typ=1 Len=1: 32    1    y