LEFT JOIN vs. LEFT OUTER JOIN in SQL Server

Question

What is the difference between LEFT JOIN and LEFT OUTER JOIN?

Answer 1

I find it easier to think of Joins in the following order:

• CROSS JOIN - a Cartesian product of both tables. ALL joins begin here
• INNER JOIN - a CROSS JOIN with a filter added.
• OUTER JOIN - an INNER JOIN with missing elements (from either LEFT or RIGHT table) added afterward.

Until I figured out this (relatively) simple model, JOINS were always a bit more of a black art. Now they make perfect sense.

Hope this helps more than it confuses.