How do I use joins in SQL?

How do I use joins in SQL?

In SQL, joins are used to combine rows from two or more tables based on a related column. There are different types of joins like INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN. Would you like to see examples of each?

Yes, please show me an example of an INNER JOIN.

Sure! An INNER JOIN returns records that have matching values in both tables. For example:

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

This query retrieves employee names along with their corresponding department names.

What about a LEFT JOIN?

A LEFT JOIN returns all records from the left table and the matched records from the right table. If there is no match, NULL values are returned for columns from the right table. Here's an example:

SELECT employees.name, departments.department_name
FROM employees
LEFT JOIN departments ON employees.department_id = departments.id;

This will show all employees, even those who are not assigned to any department.

Thanks! Can you explain the difference between INNER JOIN and LEFT JOIN?

Certainly! The main difference is that an INNER JOIN only returns rows with matching values in both tables, while a LEFT JOIN returns all rows from the left table and matched rows from the right table, filling in NULLs where there are no matches.