“JOIN” is an SQL keyword used to query data from two or more related tables.

Inner join (or just Join)

The most frequently used clause is INNER JOIN. This produces a set of records which match in both the user and course tables.

Left join

This produces a set of records which matches every entry in the left table regardless of any matching entry in the right table.

Learning Resources

• Here is a nice youtube tutorial.
• Understanding JOINs in MySQL and Other Relational Databases article.