PostgreSQL — Where

Q: What is Where in PostgreSQL?

Where is a fundamental concept in PostgreSQL. This lesson explains it step by step with clear examples, making it easy for beginners to understand.

Q: How do I learn Where?

Start by reading the explanation above, then try the code examples. Practice by modifying the examples and experimenting with different values. Hands-on practice is the best way to learn Where.

Q: Why is Where important in PostgreSQL?

Where is essential for PostgreSQL development. Understanding this concept will help you write better code and solve real-world problems more effectively.

Basic WHERE

SELECT * FROM users WHERE id = 1;
SELECT * FROM users WHERE name = 'John';

Comparison Operators

Operator	Description
=	Equal
!= or <>	Not equal
>	Greater than
<	Less than
>=	Greater or equal
<=	Less or equal

Logical Operators

-- AND
SELECT * FROM users WHERE age > 18 AND active = true;

-- OR
SELECT * FROM users WHERE country = 'USA' OR country = 'UK';

-- NOT
SELECT * FROM users WHERE NOT active;

IN

SELECT * FROM users WHERE country IN ('USA', 'UK', 'Canada');

BETWEEN

SELECT * FROM users WHERE age BETWEEN 18 AND 30;

LIKE

SELECT * FROM users WHERE name LIKE 'J%';    -- Starts with J
SELECT * FROM users WHERE name LIKE '%son';  -- Ends with son
SELECT * FROM users WHERE name LIKE '%oh%';  -- Contains oh

IS NULL

SELECT * FROM users WHERE email IS NULL;
SELECT * FROM users WHERE email IS NOT NULL;

Mini Practice

Use comparison operators
Use logical operators
Use IN and BETWEEN
Use LIKE pattern matching

Up Next

Continue with Update — updating data.

Frequently Asked Questions about Where

What is Where in PostgreSQL?