SQL LEFT JOIN Explained | Keep Unmatched Rows and Handle NULLs | SQL Tutorial
In this video, you will learn how to use LEFT JOIN in SQL to combine data from multiple tables while keeping unmatched rows. This tutorial explains how LEFT JOIN works, how NULL values appear in results, and how to handle optional relationships in a simple beginner-friendly way.
Topics Covered:
• LEFT JOIN in SQL
• Keeping unmatched rows
• Understanding NULL results
• Optional relationships between tables
LEFT JOIN returns all records from the left table and matching records from the right table. If no match is found, NULL values are returned for the right table columns.
Personal Example:
Identifying missing records in personal datasets, such as contacts without addresses or expenses without categories.
Industry Example:
Companies use LEFT JOIN for data completeness checks, identifying missing relationships, and analyzing incomplete records in reporting and analytics systems.
Example SQL Query:
SELECT Customers.CustomerName, Orders.OrderID
FROM Customers
LEFT JOIN Orders
ON Customers.CustomerID = Orders.CustomerID;
This query shows all customers, including those who have not placed any orders.
This tutorial is useful for beginners learning:
SQL
Database fundamentals
MySQL
PostgreSQL
SQL Server
Data analytics basics
Understanding LEFT JOIN is essential for handling missing data, performing data quality checks, and working with real-world relational databases.
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