Introduction

I learned how to use SQL operators to filter and retrieve specific records from a database. I practised these concepts using PostgreSQL and a hospital database containing patient information such as names, ages, counties, insurance providers, departments, bills, and admission dates.

SQL operators are important because they help us retrieve meaningful information without having to examine every record manually. For example, a hospital might want to find female patients admitted to the maternity department, patients with bills above KSh 50,000, or patients whose email addresses are missing.

In this article, I will share what I learned about comparison operators, logical operators, range and list operators, NULL handling, and pattern matching in SQL.

1. Comparison Operators

Comparison operators allow us to compare values in a database.…