Can anyone tell me WHY Oracle won't allow sub-queries in outer joins?

Question

Hi,
I've recently been tasked with converting a series of InterBase dbs to Oracle.
Many of the queries in the InterBase dbs use sub-queries in outer joins. Oracle won't countenance this (01799 - a column may not be outer-joined to a subquery).
I can get around it using functions but WHY won't Oracle allow this?
SQL Server allows it, InterBase allows it (I don't know about ANSI SQL) but it seems to be a common enough technique...
I'm just curious (and also a little frustrated!).
Thanks in advance,,,

Answer 1

Hi,
>>Oracle treat an empty string as a NULL
Well, you same answer your question. Because it is empty
SGMS@ORACLE10> create table tab (cod number, name varchar2(1));
Table created.
SGMS@ORACLE10> insert into tab values (1,'');
1 row created.
SGMS@ORACLE10> insert into tab values (2,' ');
1 row created.
SGMS@ORACLE10> commit;
SGMS@ORACLE10> select cod,dump(name) from tab;
       COD DUMP(NAME)
         1 NULL
         2 Typ=1 Len=1: 32
SGMS@ORACLE10> select * from tab where name is null;
       COD NAME
         1Cheers
If you talking about language tools, for example PHP treat empty string <> of NULL values. e.g: functions like is_empty() and is_null()
Message was edited by:
Legatti