Querying Relational Databases
Relational algebra: an operational language
Relational calculus: a declarative language
- tuple relational calculus (TRC)
- domain relational calculus (DRC)
Codd:
- The two are equivalent (sort of)
- They provide a yardstick for other languages (concept of relational completeness)
SQL: influenced mostly by TRC
Query execution plans: relational algebra