How to Join Tables in MySQL to Combine Data from Multiple Tables?

MySQL Table Joins: The Complete Guide

When dealing with relational databases like MySQL, table joins are a key operation that combines data from multiple tables based on common fields. Let us explore how to join two tables in MySQL.

Tables and data

Consider the following two tables:

• services: Contains id, client and service columns.
• clients: Store id, name and email information.

Query target

Our goal is to retrieve data from the services table and retrieve the corresponding customer name from the clients table. The client column in the services table refers to the id column in the clients table.

JOIN operation

In order to connect the services and clients tables, we use the JOIN operation. The most commonly used JOIN type is LEFT JOIN, which returns all rows of the left table (services) and the corresponding rows of the right table (clients) based on matching conditions.

SQL query

The following SQL query will perform a LEFT JOIN:

SELECT * FROM services LEFT JOIN clients ON services.client = clients.id

Explanation of results

• The query retrieves all columns from the services and clients tables.
• If a service has a corresponding customer (i.e., the customer ID in the services table matches the id in the clients table), the customer's name will be displayed in the results.
• For services that do not have a corresponding customer, the name column will be null.

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