1.6 Queries in a DBMS

  • Questions involving the data stored in a DBMS are called queries.
  • Relational calculus is a formal query language based on mathematic logic and queries in this language have an intuitive, precise meaning.
  • Relational algebra is another formal query language, based on a collection of operators for manipulating relation, which is equivalent in power to the calculus.
  • A DBMS enables users to create, modify, and query data through a data manipulation language (DML).
  • The DML and DDL are collectively referred to as the data sublanguage when embedded within a host language.