Basics

1. Hello, SELECT — Selecting constants and a first query.
2. Columns & Aliases — Selecting specific columns, aliasing, schema-qualified names.
3. WHERE Filters — Common predicates, BETWEEN/IN/LIKE/IS NULL and sargability notes.
4. ORDER BY & TOP — Sorting, TOP, WITH TIES, NULLS LAST workaround.
5. CASE Expressions — Simple vs searched CASE, default branch, common patterns.
6. NULLs & 3-Valued Logic — NULL behavior, COALESCE/ISNULL, comparisons and pitfalls.
7. 🚧 DISTINCT & Deduping — Use DISTINCT and ROW_NUMBER to remove duplicates.
8. 🚧 Subqueries — Scalar, correlated, and table subqueries.
9. 🚧 EXISTS vs IN — Compare semi-joins with EXISTS and IN.
10. 🚧 CTEs — Common Table Expressions, basic and recursive.
11. 🚧 Set Operators — UNION, INTERSECT, and EXCEPT patterns.
12. 🚧 CROSS JOIN & Self Join — Cartesian products and self-joins.