The Lost Art of the Self Join

Can you solve a Sudoku with only one SELECT statement? No temporary tables, SQL extensions, stored procedures or functions, not even non-relational features such as ORDER or GROUP BY—just plain joins and predicates? You can! With a combination of (admittedly quite a few) self joins.

Before we finally have a look at this rather exotic fun example however, we concentrate on the most practical uses of joining a table to itself—beyond the classical text-book example of the employee’s table.

There exist multiple classes of problems that can be solved elegantly with a self join. Solutions that are overlooked sometimes even by more experienced developers. The session will sharpen your eyes for these problems, without diving into theory, but with simple hands-on examples that should be easy to grasp with a sound understanding of basic SQL.