Module 1: What a database is

Why we keep data in a database, not a spreadsheet: tables, rows, keys, and what a DBMS does for you.

1. Why a database, not a spreadsheet: A database keeps one checked copy of the data in tables (relations) of rows (tuples) and columns (attributes); SELECT FROM t shows a table.
2. Keys and relationships: A primary key is unique and never NULL; a foreign key must match another table's key (or be NULL); many-to-many needs a junction table with a composite key.
3. DBMS, RDBMS and SQL: A DBMS handles concurrency, integrity, security and recovery; three levels (external, conceptual, internal) give data independence; SQL = DDL + DML + DCL + TCL.

Ends with a 14-question checkpoint (80% passes).