The JOIN statement is one of the most common operations SQL developers perform. Yet in a world ruled by Inner and Left Joins, the poor Full Outer Join is like Cinderella before the ball – allowed out on only the rarest of occasions. In an (unscientific) survey I once performed of SQL developers at one Fortune 100 firm, half of the developers had never used a Full Outer Join in production code, and the rest had used it in a tiny handful of occasions.
The FULL OUTER JOIN (hereafter ‘FOJ’) is generally considered as a tool for rare corner cases