Select Count(0)
from Accounts a inner join Jdx j on a.jdx = j.id
and a.ID not in (Select ID from Skip)
There are 2 rows in Accounts, ID values 1 and 2. There is one value in Skip.ID, "1". The result of the query above is 1. When I change the join to 'left', the count is 2. Why?