Re: Full outer join to show differences

[CRPence <CRPbottle@xxxxxxxxx>]

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