Due to null propagation, the third case can produce different results than the other cases. For example, A.column1+0 produces A.column1 whereas A.column1+null produces null.

To illustrate how a LEFT JOIN works, let’s simply change INNER JOIN to LEFT JOIN in our original SELECT statement, like this: SELECT Donors.DonorID,Donors.Donorname. DonationRecords.DonationAmt ...