5.1- Introduction To Relational Database Management & SQL | relational data model tutorials

5.1- Introduction To Relational Database Management & SQL | relational data model tutorials

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The relational model was discovered by Dr. E.F. Codd. The relational model is an abstract theory of data that is based on the mathematical concept of relations. In relational database, information is stored in tabular form or in tables. So, it consists of collection of tables. We use mathematical terms in relational model. The relational model is concerned with three aspects of data: data structure, data integrity, and data manipulation


Data Structure of Relational Database
Relational model uses simple tables instead of complex tree and network structures to simplify the user’s view of the database. It is a collection of tables in which data is stored. A table is a matrix of a series of row and column intersections. Following are the basic data structures used in relational database.
1. Relation (Entity set in E-R model) : In relational model name of table is known as relation. It consists of all possible tuples.
2. Tuple (Entity in E-R model) : Single row of any relation is known as tuple.
3. Attributes (Same in E-R model) : These are the characteristics of any relation.
4. Domain (Same in E-R model) : Domain is the set of all permitted values or information about any attributes. For example in relation Employee, domain for attribute EmpName is (Deepak, Vinay, Gaurav, Rajiv).
5. Tuple variable (Value in E-R model) : Tuple variable is the part of tuple or row, which is information or data stored in relation for any attribute.
This is not allowed because EID is a primary key
6. Degree : Number of columns in any relation is known as its degree.
7. Cardinality : Number of rows in any relation is known as its cardinality Notes Link:
http://www.tutorialsspace.com/Download-Pdf-Notes/DBMS-Notes.aspx