Question

How do i write a query that will join two tables using an Or operator
For example:

select upc,ean,productName
from maintable m1 left join maintable2 m2
on m2.upc = m1.upc OR m2.ean = m1.ean

Answer 1

Well, you can try using a UNION.

select upc,ean,productName
from maintable m1 left join maintable2 m2
on m2.upc = m1.upc
union
select upc,ean,productName
from maintable m11 left join maintable m22
on m22.ean = m11.ean

Does that work out for you? By default, the UNION operator will only return distinct rows, so do not worry about returning duplicates.