Anyone know what this is?
I just got an email…
“Yes, I know about this problem. This is LEFT JOIN problem.”
Anyone care to guess what that particular problem may be? Super exotic problems. How cool is that? 
…
OK. Here’s a hint from someone answering a similar question at a forum…
“This how it works: first you have a table specified with FROM. Then you get a new table (conceptually) by with JOIN. When you use a LEFT JOIN all rows in the left tables are included, and the columns from the right table as NULL.
Then you apply a WHERE clause on this table and filter rows with the conditions you have. With the condition on D.Dealer_code, all rows with NULL goes out the window.
This gives a couple of ways to fix this. The most common and probably the best is to move the condition on Dealer_code to the ON part.”
… to which the guy who asked the original question replies…
“Cool. Knew I’d missed something simple. Just having a bad day. Thanks !”
LOL. There was something simple in there?
It must be me, then. 
November 7th, 2007 at 6:01 pm
That’s definitely database talk. It’s part of how you pull the data out of the tables and actually put it together to be used. I recently had some database problems myself because the code was a little messed up. It was a JOIN problem too.
November 8th, 2007 at 11:08 am
“Get me a list of everyone on X mailing list that has not yet received Y email” is the type of problem which this style of query can answer:
SELECT * FROM users LEFT JOIN user_received_email ON ure_usid = us_id WHERE ure_id IS NULL AND ure_emailid = $email_id
We used to use this in an old company as an SQL test for potential new hires. Its a pretty useful one to know.
November 8th, 2007 at 12:51 pm
LOL. Hi Alex!
I did wonder if that blog post would bring you out of hiding.
How are things with you?
Neil.