0 to Hero SQL — Stage 2: Joins and shaping
Joins and the conditions that quietly change them, subqueries and CTEs, set operations, and window functions — including the default frame that catches almost everybody once.
Twenty questions on the second stage: joins, subqueries and CTEs, set operations, and window functions.
Two of these — the LEFT JOIN with a WHERE on the right table, and the default
window frame — are mistakes almost every SQL author makes once and then never again.
If you get them wrong here, that is the cheapest place to do it.
You get a score, not a list of what you missed.
Leaderboard
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