I have these tables :
I don't know how I can write a statement, that takes emails from Table "Firm", that have Location_id = '1' and Category_id = '130';
I know that I should use JOINs, but I'm not sure how to go from there.
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you need to try something before posting questions, that's one of the easiest joins you might face in your lifemamdouh alramadan– mamdouh alramadan2014-02-17 15:28:14 +00:00Commented Feb 17, 2014 at 15:28
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I tryed something SELECT Firm.email FROM Firm INNER JOIN FirmID ON FirmID.location_id = '1' AND FirmID.category_id = '130';Vladson– Vladson2014-02-17 15:29:54 +00:00Commented Feb 17, 2014 at 15:29
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3 Answers
SELECT Firm.email
FROM Firm
INNER JOIN FirmID ON Firm.firma_id = FirmID.firma_id
WHERE FirmID.location_id = '1'
AND FirmID.Category_id = '130'
Comments
Should be as simple as doing the following:
SELECT email
FROM Firm, FirmID
WHERE Firm.firma_id = FirmID.firma_id
AND FirmID.location_id = 1
AND FirmID.category_id = 130;
It does a join behind the scenes, but can be a bit clearer to understand than using the JOIN keyword.
4 Comments
Raphaël Althaus
I really wouldn't advise to use that syntax instead of the join one.
U W
Could you explain why? My understanding was that it was no less efficient than explicitly using the JOIN keyword, as SQL still does a join. Thanks
Raphaël Althaus
for example : stackoverflow.com/questions/1018822/…
U W
Thanks for clarifying your point. However, I think the outcome of that particular question is that the two are synonyms - the advantages of either option (in a case as simple as this) are stylistic. I was just trying to help the OP understand what a join meant :-)
You could do:
SELECT f.email
FROM Firm f
WHERE f.firma_id =
(
SELECT ff.firma_id
FROM FirmID ff
WHERE ff.location_id = 1
AND ff.category_id = 130
)
Using an inner select.
But using JOINS is in the long term the way to go, what have you tried and what's not working?
