- 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.