The Case Files
SQL concepts explained the way we teach them — as investigations.
WHERE vs HAVING in SQL: The Alibi Problem
WHERE filters rows, HAVING filters groups — and swapping them is why Invalid use of group function keeps happening. Here's exactly when to use each.
SQL Order of Execution: Your Query Doesn't Run Top to Bottom
You wrote SELECT first. SQL read it sixth. Here's the real order clauses run in — and why it explains three of the most baffling beginner errors.
Prefer to learn by doing? Start Case 1 — no account, no setup. Or follow the SQL learning roadmap.