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.