SQL WHERE Keyword

Introduction

The WHERE keyword is fundamental in SQL. It allows you to filter the results of a query, showing only the rows (records) that meet a specific condition. This makes your queries more precise and efficient.

Basic Usage

The WHERE clause is used with the SELECT statement (and others like UPDATE and DELETE) to filter data.

Example 1: Filtering Text Data

This example selects all customers from Mexico from a "Customers" table.

SELECT * FROM Customers WHERE Country='Mexico';
            

(This output will show all columns (*) for customers where the Country column is 'Mexico'.  The specific data depends on your 'Customers' table.)
            

Example 2: Filtering Numeric Data

This example selects a specific customer using their numeric CustomerID.

SELECT * FROM Customers WHERE CustomerID=1;
            

(This will display all columns (*) for the customer with CustomerID 1.  The data will depend on your 'Customers' table.)
            

Important Notes

• SQL uses single quotes around text values (although some database systems might allow double quotes).
• Numeric fields should not be enclosed in quotes.
• The WHERE clause isn't limited to SELECT statements; it's also used with UPDATE, DELETE, and other SQL commands.

Comparison Operators

The WHERE clause uses comparison operators to define the conditions: