SQL

1. SQL syntax

   Lexical structure, identifiers and quoting, constants, operators, value expressions, function calls and NULL.

2. Data definition

   CREATE TABLE, data types, default values, ALTER TABLE, schemas and system columns.

3. Constraints

   Primary keys, foreign keys, unique, check, not-null and exclusion constraints, referential actions.

4. Data manipulation

   INSERT, UPDATE, DELETE, RETURNING and upserts.

5. Queries

   SELECT, select lists, WHERE, GROUP BY, HAVING, ORDER BY, LIMIT/OFFSET and DISTINCT.

6. Table expressions and joins

   FROM clause, inner/outer/cross joins, subqueries, LATERAL and table functions.

7. Combining queries

   UNION, INTERSECT and EXCEPT set operations.

8. WITH queries (CTEs)

   Common table expressions, recursive queries and data-modifying CTEs.

9. Data types

   Numeric, character, date/time, boolean, enum, array, JSON, UUID and range types.

10. JSON types and functions

    json vs jsonb, operators, path queries and indexing.

11. Functions and operators

    Built-in comparison, logical, string, date/time, conditional, array and subquery expressions.

12. Aggregate functions

    COUNT, SUM, AVG, FILTER, GROUP BY with grouping sets and ordered-set aggregates.

13. Window functions

    OVER, PARTITION BY, ORDER BY frames, ranking, lag/lead and running totals.

14. Type conversion

    Implicit and explicit casts, operator and function type resolution.

15. Views

    Creating views, updatable views and materialized views.

16. Indexes

    B-tree, hash, GIN, GiST and BRIN indexes, multicolumn, partial and expression indexes, index-only scans.

17. Transactions

    BEGIN/COMMIT/ROLLBACK, atomicity and savepoints.

18. Concurrency control and MVCC

    Isolation levels, MVCC, row and table locking, deadlocks and serialization failures.

19. Performance tips

    EXPLAIN and EXPLAIN ANALYZE, planner statistics, bulk loading and query tuning.

20. Table partitioning

    Range, list and hash partitioning, partition pruning and inheritance.

21. Privileges and row security

    GRANT/REVOKE, roles and row-level security policies.

22. Full text search

    tsvector, tsquery, dictionaries, ranking and GIN indexing for text search.

Each section links to the official page. Titles and summaries by Extra Credit; the docs belong to their authors.