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MySQL: Check if two values are equal

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MySQL: Check if two values are equal

girasquid	19 Feb, 2007 - 05:00 PM Post #1
Barbarbar Joined: 3 Oct, 2006 Posts: 1,294 Thanked: 18 times Dream Kudos: 725 My Contributions	Hello, all. For a recent project, I have been tasked with taking a count of the number of rows in two MySQL tables, and then figuring out if they are equal. I know that I can do this by using two queries, retrieving the values, and comparing them, but I'm wondering: is there a way to do it that uses only one query? Thanks, Girasquid
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snoj	RE: MySQL: Check If Two Values Are Equal 19 Feb, 2007 - 05:24 PM Post #2
Fell off the face of the earth Joined: 31 Mar, 2003 Posts: 3,325 Thanked: 9 times Dream Kudos: 750 My Contributions	Sounds like homework to me, but to answer your question, yes, it can be done in one query.
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girasquid	RE: MySQL: Check If Two Values Are Equal 19 Feb, 2007 - 05:33 PM Post #3
Barbarbar Joined: 3 Oct, 2006 Posts: 1,294 Thanked: 18 times Dream Kudos: 725 My Contributions	QUOTE(hotsnoj @ 19 Feb, 2007 - 06:24 PM) Sounds like homework to me, but to answer your question, yes, it can be done in one query. It isn't homework, but this is the query I've tried and had fail: CODE (SELECT COUNT() FROM user_answered WHERE user = ?) = (SELECT COUNT() FROM questions) That throws an error about my SQL syntax, and I'm also pretty sure I'm looking for something else syntactically to do this. EDIT: I figured out how to do it on my own, it turns out I needed to put a SELECT in front of that query, so that it looks like this: CODE SELECT (SELECT COUNT() FROM user_answered WHERE user = ?) = (SELECT COUNT() FROM questions) Which will return a 0 if they don't match, and a 1 if they do. This post has been edited by girasquid: 19 Feb, 2007 - 06:06 PM
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Trogdor	RE: MySQL: Check If Two Values Are Equal 20 Feb, 2007 - 03:21 AM Post #4
D.I.C Addict Joined: 6 Oct, 2006 Posts: 549 Thanked: 4 times Dream Kudos: 125 My Contributions	Great that you found it out yourself. Tip: You can change the output behaviour with the CASE WHEN construct. (for example to give 'Y' or 'N' instead of 1 or 0)
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