[development] SQL question.

[Earl Miles]

Gordon Heydon 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';
> 
> So basically I want it to return.
> 
> a	b	a	c
> 1	1	null	null
> 2	2	2	A
> 
> etc.
> 
> Or do I need to 2 selects and merge them. When I do this now I get more
> of an inner join instead of a left join. I am not sure how I say "or
> doesn't exist".
> 
> Thanks in advance.
> Gordon.

...WHERE b.c = 'A' OR b.c IS NULL;