MeritKeep

NULL semantics

Three-valued logic, IS NULL vs = NULL, NULL propagation through arithmetic and aggregation, COALESCE and NULLIF.

foundational~1.5hWe mark it against a checklist you can read first
The barWhat counts as knowing this

Predict and control how NULLs affect a filter, a join and an aggregate

That sentence is the bar. It only counts once your work shows you can do it. Reading about it does not.
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Up to 4 questions on this skill alone, marked against the bar beside this. It stops as soon as the answer is clear. No account, and your answers are not kept.

01 · Prerequisites

You'll need these first

03 · What comes next

What it unlocks

Start on SQL & Data Analysis

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