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How to find a bad query
by
24 Feb 2002
I've been testing a hack I've been working on. At one point during the testing, I received a MySQL error message stating there was a problem with a query. It said what the query was, but as you've probably noticed in these error messages, it only gives a line number of '1'. The problem here was that I had four of the exact same query throughout the code, and I couldn't tell which one was causing the problem. The specific problem was that in the WHERE part, it was written like "WHERE field=$variable", and $variable didn't have a value. The problem really wasn't the query itself, it was the code before it that was supposed to generate a value for $variable. So the problem was how to quickly find out which of the four identical queries had some bad code before it. Then I realized how to do it. In the first query, I put a "and 1=1" at the end of the WHERE part, so it was like "WHERE field=$variable and 1=1". For the next one, I did 2=2, and so on, for all four. Because 1 always equals 1, putting that bit in has absolutely no effect whatsoever on how the code or query works. Basically, you're putting it there as a marker. This way, when the error message showed up and the query was quoted, it would include the marker (the "and x=x" part), and that would show me which query had the bad code before it. Maybe this was basic or nothing new for a lot of you, but I'm still kind of new at this, and I'm glad I figured it out before I had to carefully examine all the code I would have had to look at, because that would have been a pain in my ass.  But if this helps even just one of you, it was worth it for me to post this.
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