SQL

In SQL, when writing queries to check if column values are NULL it is common to attempt WHERE conditions using ‘column_name = NULL’ or ‘column_name != NULL’ or ‘column_name <> NULL‘. Trying to check if a column is NULL using equal or not equal will actually provide incorrect results. This article will cover how to …

SQL – How To Write Queries For NULL Values – IS NULL And IS NOT NULL Read More »

This tutorial will explain why a self join is used in SQL and how to create a self join query. Knowledge of how to write inner, left, and right joins is needed before continuing with this tutorial. This tutorial uses MySQL as the database management system in the examples. However, many other DBMS’s such as …

SQL – Self Join Explained Read More »