What is Relational Model?Relational Model (RM) represents the database as a collection of relations. A relation is nothing but a table of values. Every row in the table represents a collection of related data values. These rows in the table denote a real-world entity or relationship.
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The table name and column names are helpful to interpret the meaning of values in each row. The data are represented as a set of relations. In the relational model, data are stored as tables. However, the physical storage of the data is independent of the way the data are logically organized.
Some popular Relational Database management systems are:DB2 and Informix Dynamic Server – IBMOracle and RDB – OracleSQL Server and Access – Microsoft
In this tutorial, you will learn
Relational Model ConceptsAttribute: Each column in a Table. Attributes are the properties which define a relation. e.g., Student_Rollno, NAME,etc.Tables – In the Relational model the, relations are saved in the table format. It is stored along with its entities. A table has two properties rows and columns. Rows represent records and columns represent attributes.Tuple – It is nothing but a single row of a table, which contains a single record.Relation Schema: A relation schema represents the name of the relation with its attributes.Degree: The total number of attributes which in the relation is called the degree of the relation.Cardinality: Total number of rows present in the Table.Column: The column represents the set of values for a specific attribute.Relation instance – Relation instance is a finite set of tuples in the RDBMS system. Relation instances never have duplicate tuples.Relation key – Every row has one, two or multiple attributes, which is called relation key.Attribute domain – Every attribute has some pre-defined value and scope which is known as attribute domain
In the above-given example, CustomerName=”Amazon” is selected
Best Practices for creating a Relational ModelData need to be represented as a collection of relationsEach relation should be depicted clearly in the tableRows should contain data about instances of an entityColumns must contain data about attributes of the entityCells of the table should hold a single valueEach column should be given a unique nameNo two rows can be identicalThe values of an attribute should be from the same domain
Advantages of using Relational ModelSimplicity: A Relational data model in DBMS is simpler than the hierarchical and network model.Structural Independence: The relational database is only concerned with data and not with a structure. This can improve the performance of the model.Easy to use: The Relational model in DBMS is easy as tables consisting of rows and columns are quite natural and simple to understandData independence: The Structure of Relational database can be changed without having to change any application.Scalable: Regarding a number of records, or rows, and the number of fields, a database should be enlarged to enhance its usability.
Disadvantages of using Relational ModelFew relational databases have limits on field lengths which can’t be exceeded.Relational databases can sometimes become complex as the amount of data grows, and the relations between pieces of data become more complicated.Complex relational database systems may lead to isolated databases where the information cannot be shared from one system to another.
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