Overview of Database Management System (DBMS) – Part 5

Information Modeling

Designing the construction of a database is the information modeling: a gathering of theoretical tools for labeling information, information associations, information semantics, as well as reliability constrictions.

In the direction of demonstrating the notion of information modeling, two (2) information models have been outlined: the entity – relationship (ER) model and the relational model. Mutually both of the models deliver a method to define the policy of a database at the logical level.

The Entity – Relationship (ER) Model

The entity-relationship (ER) information model is grounded on an awareness of an actual world which contains a group of rudimentary items, known as entities, as well as of relationships between these items. An entity is an “item” or else a “thing” in the actual world which is unique from additional items. For an instance, every single individual is an entity, plus bank account could be well-thought-out as the entities. The complete logical design (schematic) of a database can be conveyed realistically by an ER illustration.

Entities are defined in a database by means of a group of columns or attributes. For an instance, the columns or attributes Account_Number as well as Balance possibly will define one (1) specific account in a bank, plus they create columns or attributes of the account entity group. In the same way, columns or attributes Customer_Name, Customer_Address plus Customer_City possibly will define a customer entity.

An added column or attribute Customer_ID is castoff to exclusively recognize customers, as it might be probable to have two (2) customers with the identical name, address, as well as city. An exclusive customer detector should be allotted to every single customer.

A relationship is a connection between more than few entities. For an instance, Depositor relationship links a customer with every single account that he or she has in the bank. The group of every entities of the identical nature plus the group of all associations of the identical type are known as an entity group and relationship group correspondingly.

Relational Modeling

The relational modeling practices a group of tables or relations to signify both the information as well as the associations between that information. Every single table or relation has numerous columns or attributes, plus every single column or attribute has a exclusive name assigned.

The information is organized in such a manner in relation that it is visually embodied in a two (2) dimensional table or relation. The information is added into the table or relation in the form of rows or tuples. A row or tuple is designed by means of one or more than one columns or attributes, which are castoff as rudimentary structure blocks in the development of numerous languages which are castoff to get significant data. There can be whatever number of rows or tuples in the table or relation; however every row or tuple have stable as well as identical columns or attributes with changing date. The relational modeling is applied in database where a relation is signified by means of a table (which are also known as relation), a tuple is also known as row, an attribute is also known as a column, attribute or column name is the name of the column like ‘Account_Number’, ‘Balance’, ‘Customer_Name’, ‘Customer_Address’, ‘Customer_City, ‘Customer_ID’ column or attribute data has the data for column or attribute in the row or tuple. Constrictions are smeared on the table or relation plus form the logical schema. With the intention of enabling the selection of a specific row or tuple from the table or relation, the columns or attributes names are used, plus to accelerate the selection of the rows or tuples certain columns or attributes are demarcated exclusively to practice them as indexes, which assistances in searching the necessary information as soon as possible. Every relational algebraic action like – Select, Join, Product, Intersection, Union, Project, Difference, Merge and Division can be done on the relational database model too. Actions on the relational database model are simplified with the assistance of many provisional expressions, numerous key attributes or columns, and pre – defined constrictions.

Additional Information Modeling

The object oriented information modeling is additional information modeling which has realized swelling consideration. The object oriented modeling can be understood as encompassing the ER modeling with concepts object oriented information modeling. The object relational information modeling syndicates structures of the object oriented information modeling as well as relational information modeling. Semi organized information modeling let the requirement of information where separate information objects of the identical form might have dissimilar group of columns or attributes. This is in difference with the information modeling stated previous, where every single information piece of a specific form should have the identical group of columns or attributes. The extensible markup language (XML) is extensively castoff to signify semi organized information.

Factually, two (2) added information modeling, the network information modeling as well as the hierarchical information modeling, headed the relational information modeling. These modeling were knotted diligently to the fundamental application, plus it complex the job of modeling information. Consequently they are rarely castoff at the present time, apart from for the old database programs which are still in use in a number of places.

In the upcoming part we will be discussing the two (2) Database Operation Languages which are Data Definition Language (DDL) and Data Manipulation Language (DML).