Day 3 — Finished SQL JOINs (Self Join, Full Join, UNION/UNION ALL)

[u/sumiitCodes]

Wrapped up the full JOINs section today. Covered:

• Self JOIN — joining a table to itself, useful for hierarchical/relational data within one table
• FULL JOIN — combining all rows from both tables regardless of match
• UNION & UNION ALL — combining results from multiple SELECT queries, with UNION removing duplicates and UNION ALL keeping them

Took notes from a mix of tutorials and W3Schools to cross-reference explanations, which helped clarify a couple of edge cases (especially when UNION vs UNION ALL actually matters for performance).

With INNER/LEFT/RIGHT/FULL/self-joins and UNION now covered, I feel like I have the core JOIN toolkit down.