Database Management Systems

A book-shaped table of contents for DBMS: relational foundations through SQL mastery, storage internals, transactions, distributed databases, NoSQL, and MAANG interview prep — cross-linking existing system-design/patterns notes instead of duplicating them.

4 — Aggregation

Covers GROUP BY, HAVING, aggregate functions, and multi-dimensional aggregation via ROLLUP, CUBE, and GROUPING SETS.

5 — Subqueries

Covers scalar and correlated subqueries and the EXISTS, NOT EXISTS, ANY, and ALL predicates.

6 — Common Table Expressions

Covers recursive and non-recursive common table expressions and their use in querying hierarchical data.

7 — Window Functions

Covers the OVER() clause and ranking/offset window functions — ROW_NUMBER, RANK, DENSE_RANK, LEAD, LAG, FIRST_VALUE, and LAST_VALUE.