DBMS/Relational Database

A database based on relational algebra or relation model is called relation database

Relational data model

 * relation : a table in a relational database is called relation in the mathematical language of relational algebra. relations are unordered.
 * attribute : column of a table in database table is called attributes. columns or attributes have names.
 * domain : set of permissible values for an attribute ( or column) is called domain.
 * tuple : a row in the database table is called tuple in the mathematical language of relational algebra. order of tuples in a relation has no significance.
 * database : a database is a collection of multiple relations.
 * schema : a database design is called schema, alternatively, a schema can refer to namespace within a database.
 * cardinality of a relation : number of tuples in a relation is called cardinality of the relation.

Normalization theory deals with design of relational database schema.

Keys

 * key : any subset of a relation is called key.
 * super key : a key is called super key if it is sufficient to identify a unique tuple of a relation.
 * candidate key : a minimal super key is called candidate key i.e. no proper subset of a candidate key is super key.
 * primary key : a candidate key chosen as a principal to identify a unique tuple of a relation.It Restrict User Inputs like "Null Values", "Duplicate Values" etc.
 * foreign key : a key of a relation which is a primary key of some other relation in the relational schema.