SQL Antipatterns, Volume 1

If you try and take a cat apart to see how it works, the first thing you have in your hands is a non-working cat.

Douglas Adams

Chapter 6Entity-Attribute-Value

“How do I count the number of rows by date?” This is an example of a simple task for a database programmer. This solution is covered in any introductory tutorial on SQL. It involves basic SQL syntax:

EAV/intro/count.sql

SELECT date_reported, COUNT(*)
FROM Bugs
GROUP BY date_reported;

The simple solution assumes two things:

• The bug date is stored only in the column named Bugs.date_reported on every row of the table.

• Values can be compared to one another so that GROUP BY can accurately group dates with equal values together.

You can’t always rely on those assumptions. ...