Your right. You and Roger hit it on the head. Stupid me miss read Roger's original post.
Last night I was banging my head on the left and right joins but I didn't understand it until I read Gerald's last note. Plus I didn't realize you can put two conditions in the ON clause which is why I didn't get Roger's post.
Thank you very much guys. You saved the day.
Joe
On Friday, January 16, 2004, at 12:31 PM, gerald_clark wrote:
That is the whole point of a left join.
It joins to a null record when the appropriate right record does not exist.
sulewski wrote:
Roger,
Thank you for the feedback. But unfortunately this doesn't work. The problem is that rid will never be null. I'm trying to find the item in tab1 where a link cannot be created in tab2 where tab2.rid=tab1.id and tab2.vid=46 because there is no record in tab2. Not that the record may have null values. I did try what you said and it didn't work.
But thanks,
Joe
On Friday, January 16, 2004, at 11:49 AM, Roger Baklund wrote:
* sulewski [...]
What I need is all records in table 1 that will not link to table 2 such that relid=rid and vid=46
Sounds like a job for LEFT JOIN...?
Join to the rows you do NOT want with a left join, and put as a condition in
the WHERE clause that a joined column IS NULL. Something like this:
SELECT tab1.* FROM tab1 LEFT JOIN tab2 ON tab2.rid=tab1.id AND tab2.vid=46 WHERE tab2.rid IS NULL
-- Roger
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