SQL (ISO/IEC 9075)

1. SQL conformance and features

   Which parts of ISO/IEC 9075 core and optional features are supported.

2. Lexical structure

   Identifiers, keywords, constants and operators.

3. Data types

   Standard SQL types: numeric, character, date/time, boolean.

4. Table expressions and joins

   FROM, JOIN types, WHERE, GROUP BY and HAVING.

5. Constraints

   Primary keys, foreign keys, unique, check and not null.

6. Common table expressions

   WITH queries and recursive CTEs.

7. Window functions

   OVER, PARTITION BY and frame clauses.

8. Transactions and isolation levels

   READ COMMITTED, REPEATABLE READ and SERIALIZABLE.

9. Three-valued logic and NULL

   NULL comparison semantics and IS DISTINCT FROM.

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