Standard comparison operators in PostgreSQL

Introduction

We use comparison operators to check if values are equal, bigger, smaller, or different. This helps us find or filter data in a database.

Finding all customers older than 30 years.

Checking if a product price is less than 100 dollars.

Selecting orders that were made on a specific date.

Filtering employees who are not in a certain department.

Comparing two columns to find matching records.

Syntax

PostgreSQL

value1 = value2
value1 <> value2
value1 != value2
value1 > value2
value1 < value2
value1 >= value2
value1 <= value2

= means equal to.

<> and != both mean not equal to.

Examples

Selects employees who are exactly 25 years old.

PostgreSQL

SELECT * FROM employees WHERE age = 25;

Finds products with a price greater than 50.

PostgreSQL

SELECT * FROM products WHERE price > 50;

Gets orders that are not shipped yet.

PostgreSQL

SELECT * FROM orders WHERE status <> 'shipped';

Finds users who signed up on or before January 1, 2023.

PostgreSQL

SELECT * FROM users WHERE signup_date <= '2023-01-01';

Sample Program

This creates a table of employees, adds three people, then selects those who are 30 or older.

PostgreSQL

CREATE TABLE employees (id SERIAL PRIMARY KEY, name TEXT, age INT);
INSERT INTO employees (name, age) VALUES ('Alice', 30), ('Bob', 25), ('Carol', 35);
SELECT name FROM employees WHERE age >= 30;

Important Notes

Use = for exact matches, and <, >, <=, >= for range checks.

Both <> and != mean 'not equal' and can be used interchangeably.

Comparison operators work with numbers, text, dates, and more.

Summary

Comparison operators help filter data by comparing values.

= means equal, <> or != means not equal.

<, >, <=, >= check if values are smaller, bigger, or equal.