Joins (INNER, LEFT, RIGHT, FULL)

Summary

Combining rows from two or more tables based on a shared key — INNER returns only matches, LEFT keeps all rows from the first table, RIGHT the second, FULL keeps everything from both.

• 1Draw a Venn diagram for each join type before writing the query.
• 2Practice a LEFT JOIN to find rows in one table with no match in another (e.g. users with no orders).
• 3Write the same question as an INNER JOIN and a LEFT JOIN and compare row counts.