Antipattern: Solve a Complex Problem in One Step

SQL is a very expressive language — you can accomplish a lot in a single query or statement. But that doesn’t mean it’s mandatory or even a good idea to aim to solve every problem in one line of code. Do we have this habit with any other programming language we use? Probably not.

Unintended products

One common consequence of producing all our results in one query is something called a Cartesian product. This happens when two of the tables in the query have no condition restricting their relationship. Without such a restriction, the JOIN for the two tables pairs each row in the first table to every row in the other table. Each such pairing ...