Q: Explain the difference between INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL OUTER JOIN.

A: INNER JOIN -> The default option when the keyword JOIN is plainly used. It means that when the two tables are merged, discard anything that's not found in both tables.

LEFT JOIN -> like INNER JOIN + ALL records from the LEFT table (joined value will appear as NULL for these records)

RIGHT JOIN -> like LEFT JOIN, but flip which table gets ALL records joined

OUTER JOIN -> LEFT JOIN + RIGHT JOIN
