MySQL Inner Join

The INNER JOIN in MySQL is a type of join operation that returns only the rows for which there is a match between the columns in the tables being joined. It combines rows from two or more tables based on a specified condition, and it excludes rows from both tables that do not have corresponding values in the other table.

Here’s the basic syntax for an INNER JOIN:

SELECT columns
FROM table1
INNER JOIN table2 ON table1.column_name = table2.column_name;

Let’s break down the components of this syntax:

• SELECT columns: Specifies the columns you want to retrieve from the joined tables. You can select specific columns from both tables.
• FROM table1: Indicates the first table you want to include in the join.
• INNER JOIN table2: Specifies the second table you want to join with the first table.
• ON table1.column_name = table2.column_name: This is the join condition. It defines which columns in each table are used to match rows from the two tables.

Here’s a practical example of using an INNER JOIN. Suppose you have two tables, employees and departments, and you want to retrieve the names of employees and their corresponding department names based on a shared department_id:

SELECT employees.employee_name, departments.department_name
FROM employees
INNER JOIN departments ON employees.department_id = departments.department_id;

In this example, the INNER JOIN combines rows where the department_id values match in both tables. This produces a result set that includes the names of employees and their corresponding department names, but only for employees who belong to a department.

An INNER JOIN is useful when you want to retrieve data only when there is a match in both tables, ensuring that you get related information without including unrelated rows. It is one of the most common types of joins used in SQL queries.