If you only want to update values in table A when there are matching records in table B, then an inner join is the way to go. If you have calculations that need to vary based on optional data, the ...

In this SQL Server tip, Arthur Fuller explains the effects of NULLs, and the different results obtained by inner and outer JOINs.

In this example, the LEFT JOIN answers the following business question: ... most implementations of SQL support the INNER JOIN, LEFT JOIN, and RIGHT JOIN constructs.