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On 3/10/11 7:08 AM, David FOXWELL wrote:
Joe, I was already trying IFNULL () but I get an error message.

On 3/10/11 6:23 AM, Joe Pluta wrote:
select * from before b
full outer join after a
on b.id=a.id
where a.data<>b.data
or ifnull(b.data)

The ifnull() is a scalar function requiring two expressions; i.e. the ifnull() is not a predicate, and thus when used in that context must appear as a scalar in a predicate. The IS NULL predicate is used to check for database NULL values. However assuming the second expression were ensured to not be the NULL value, e.g. a literal as the second expression in the ifnull() scalar function, then an equal sign comparing to that literal can [if the literal does not exist as data] effect the equivalent of the IS NULL predicate; i.e. WHERE ... OR ifnull(b.data,'*N')='*N'

Regards, Chuck

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