Bill Dodson wrote:
I am using version 4.0.12-nt on a Windows 2000 machine.
I have 4.1.11.
I have noticed some difference in the way SET and SELECT create
variables. The following statements do not work the way I would expect.
SELECT @neededStep := 10;
SELECT @startOfCenter := 7;
SELECT @returnData :=
IF(@neededStep <= @startOfCenter,
CONCAT(@neededStep, ' <= ', @startOfCenter),
CONCAT(@neededStep, ' > ', @startOfCenter)
);
In the above example @returnData ends up being '10 <= 7', but when
@neededStep is less than 10 the expected results are found. (could this
be because @neededStep is stored as text and not a number?)
I get '10 > 7'.
In the next example @returnData ends up being '10 > 7', as expected.
This seems to work for all values of @neededStep I have tested.
SET @neededStep := 10;
SET @startOfCenter := 7;
SELECT @returnData :=
IF(@neededStep <= @startOfCenter,
CONCAT(@neededStep, ' <= ', @startOfCenter),
CONCAT(@neededStep, ' > ', @startOfCenter)
);
This also gives me '10 > 7'.
It would seem that SET is a better way to create variables from constant
values, but I would like to understand why. Does anybody know what is
happening here?
I expect it's a bug which has since been fixed (though I didn't check the bugs
db to be sure). You are using a very old version of mysql -- 4.0.12 was
released in March, 2003. The current version in the 4.0.x series is 4.0.25.
You can read the rather impressive list of bugs fixed since 4.0.12 in the
manual <http://dev.mysql.com/doc/mysql/en/news-4-0-x.html>. I'd suggest
upgrading.
Thanks for your time!
bill
Michael
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