Database: a set of interrelated, centrally coordinated files
DBMS (Database Management System): an interface between the database and applications
Database system: the database + DBMS + applications
DBA (Database administrator): person responsible for the database
Schemas: the logical structure of database
Conceptual-level: organization-wide view of the entire database
External-level: a set of individual user views of portions of a database (subschema)
Internal-level: low-level view; details about data storage
Data dictionary: information about the structure of the database
DBMS languages: DDL (definition), DML (manipulation), DQL (query), Report writer
Relational Databases
Data model: an abstract representation of the contents of a database
Relational data model: database stored in tables (relations)
Tuple: a row in a relation (entry)
Primary key / Foreign key / Non-key
If all data stored in one table
Update anomaly, insert anomaly, delete anomaly, waste of space
Requirements of a RD
- All data single-valued
- Primary keys not null
- Foreign key values correspond to self-titled primary key
- Non-keys describe characteristics identified by the primary key
