Understanding Inner Join in SQL

In SQL, the INNER JOIN clause is used to combine rows from two or more tables based on a related column between them. It retrieves rows from both tables that satisfy the join condition.

Syntax

The basic syntax for an INNER JOIN in SQL is as follows:

SELECT column_name(s)
FROM table1
INNER JOIN table2
ON table1.column_name = table2.column_name;

Example

Consider the following two tables, employees and departments:

employees table: | emp_id | emp_name | dept_id | |——–|———-|———| | 1 | John | 101 | | 2 | Alice | 102 | | 3 | Bob | 101 |

departments table: | dept_id | dept_name | |———|———–| | 101 | HR | | 102 | IT |

To retrieve the names of employees along with their department names, you can use the INNER JOIN as follows:

SELECT employees.emp_name, departments.dept_name
FROM employees
INNER JOIN departments
ON employees.dept_id = departments.dept_id;

This will produce the result: | emp_name | dept_name | |———-|———–| | John | HR | | Alice | IT | | Bob | HR |

In this example, the INNER JOIN combines the employees and departments tables based on the dept_id column, and retrieves the matching rows from both tables based on the common department ID.

With INNER JOIN, you can effectively retrieve only the rows for which there is a match in both tables, based on the specified condition.

For more information on the INNER JOIN clause in SQL, refer to the official MySQL documentation.

This is a simple explanation on how to use the INNER JOIN clause in SQL to combine data from multiple tables based on a related column. ```