On Sun, Aug 08, 2010 at 01:55:19AM -0700, John R Pierce wrote:
> >The condition
> >
> > and table.item = 'laptop' and table.item = 'Desktop'
> >
> >says: I want all rows where the column item has the value 'Laptop'
> >and *at the same time* has the value 'Desktop'
> >Which clearly cannot be the case (a column can only have a single value)
> >
> >So you need to join all "Laptop" rows to all "Desktop" rows to get
> >what you want.
>
> why not use OR ?
>
> ... AND (table.item = 'laptop' OR table.item='Desktop') ...
OR doesn't account for duplicates. Two laptops on the same date would
cause a false positive.
Cheers,
David.
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