Re: Test for a NULL variable
This was answered here
http://forums.mysql.com/read.php?60,40208,40208#msg-40208
but the IF...THEN...END IF; construct explained there i particularly useful if you want to conditionally execute a (list of) statements. If you want to drive an expressions value according to the 'NULLness' of another expression, you can use:
COALESCE(arg1,arg2[,argn]) : returns the first not null argument
IFNULL(input,<output if input IS NULL>)
of course,
expr IS NULL
is also valid in stuff like:
IF (expr IS NULL, <output if null>, <output if not null>)
and
CASE
WHEN expr IS NULL THEN <output if null>
ELSE <output if not null>
END
for more info see:
http://dev.mysql.com/doc/mysql/en/control-flow-functions.html
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Re: Test for a NULL variable
August 23, 2005 06:22AM
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