[development] SQL question.

Pat Collins pat at linuxcolumbus.com
Fri Feb 3 04:33:12 UTC 2006

On Fri, 03 Feb 2006 15:17:39 +1100, Gordon Heydon <gordon at heydon.com.au> wrote :

> Hi,
> I have been trying to work out a small sql issue, and I was wondering if
> someone might be able to help me.
> Basically I have 2 tables and I was to do a left join and pull out all
> rows which has a value in the right hand table or doesn't exist.
> eg.
> SELECT a.a, a.b, b.a, b.c FROM a LEFT JOIN b ON a.a = b.a WHERE b.c =
> 'A';

Your where clause is going to limit you to only rows where b.c = 'A'. 

> So basically I want it to return.
> a	b	a	c
> 1	1	null	null
> 2	2	2	A

So you will probably want to add 'OR b.a is null' (or however you have the
lack of value defined) to your WHERE above.


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