PostgreSQL: Using the OR Condition in Queries

Combine multiple conditions using the OR operator in PostgreSQL queries. This guide explains the syntax and usage of OR in WHERE clauses.

Using the `OR` Condition in PostgreSQL

PostgreSQL's `OR` condition is used in the `WHERE` clause of SQL queries to select rows where at least one of multiple conditions is true. This is a fundamental tool for flexible data retrieval, enabling you to combine different selection criteria.

Understanding the `OR` Condition

The `OR` condition combines multiple conditions. If any one of the conditions is true, the entire `OR` condition evaluates to true, and the corresponding row is included in the result set. This differs from the `AND` condition where all conditions must be true.

`OR` Condition Syntax

WHERE condition1 OR condition2 OR condition3 ...;

Examples of `OR` with Different SQL Commands

(Note: The examples below assume the existence of tables named `employee` and `car` with appropriate columns. Screenshots from the original text are not included here. Please refer to the original document for visual verification of the examples. The descriptions below aim to convey the information present in those screenshots.)

Example 1: `SELECT` with `OR` (Two Conditions)

This example retrieves employees either from 'New York' or with an `emp_id` greater than 8:

SELECT emp_id, emp_fname, emp_lname, location
FROM employees
WHERE location = 'New York' OR emp_id > 8;

Example 2: `SELECT` with `OR` (Multiple Conditions)

This example is a more complex query that retrieves cars based on multiple conditions:

SELECT car_id, car_name, car_model, car_price, car_color, body_style
FROM cars
WHERE body_style = 'coupe' OR body_style = 'wagon' OR car_price = 63890;

Example 3: `INSERT` with `OR`

This example inserts data into the `department` table based on an `OR` condition in the `WHERE` clause of the `SELECT` subquery used by the `INSERT`.

INSERT INTO departments (phone, address)
SELECT phone, address
FROM employees
WHERE emp_id < 6 OR employee_name = 'Emily Smith';

Example 4: `UPDATE` with `OR`

This example updates rows in the `customers` table based on an `OR` condition.

UPDATE customers
SET cust_name = 'Mike', cust_address = 'London', cust_age = 26
WHERE cust_id = 103 OR cust_name = 'emily';

Example 5: `DELETE` with `OR`

This example deletes rows from the `departments` table based on an `OR` condition.

DELETE FROM departments
WHERE dept_name = 'RESEARCH' OR emp_fname = 'Cena';