C4 Relational Databases

  • 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

  1. All data single-valued
  2. Primary keys not null
  3. Foreign key values correspond to self-titled primary key
  4. Non-keys describe characteristics identified by the primary key
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