Different Database Models Assignment
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Added on 2020-04-15
Different Database Models Assignment
Added on 2020-04-15
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[Different Database models][1]Hierarchical ModelIn this type of database model data elements have one-to-many relationships. Hierarchical modelis of tree like structure. Limitation of this model is many-to-many relationship does not exist.[2] Network ModelNetwork model is a type of database model in which data elements implements many to manyrelationships.
[3] Relational ModelRelational model is a type of database model in which data entities have a grid like relationshipin the form of columns and rows. Relational model graphically represents the logical relationshipof entities in order to create database.[4] Data Manipulation languageData Manipulation language (DML) is a type of computer programming language by which datais modified, added, deleted in a specified database. It is used to manipulate the data like addingnew elements to the database, retrieving through the database, deleting the unwanted orredundant data. DML commands are not permanent to database, it can be rolled back.It has three main commands namely:-1.INSERT- It is used to insert data into database tables. Syntax is INSERT into table-name values (data1,data2,..);Example-Student_idStudent_nameAgeINSERT into Student values (420, ‘John’, 20);
OutputStudent_idStudent_nameAge420John202.UPDATE- It is used to update a row. Syntax is UPDATE table-name set column-name = value where condition; Example Output- UPDATE Student set age=18 where Student_id=420;Student_idStudent_nameAge420John183.DELETE- This is used to delete data elements from a table.Syntax is DELETE from table-name;It can also be used with condition like DELETE from student where Student_id=420;Student_idStudent_nameAge[5] Data Definition LanguageData definition language (DDL) is used to change to structure of database and schema. MainlyCREATE, ALTER OR DROP commands are used in this language. CREATE command is usedfor creating new table; ALTER OR DROP is used to remove a table and its definitions.Syntax for CREATE- CREATE table-name;Syntax for ALTER or DROP- ALTER table table-name add (column name, data type); [6] Data IndependenceData independence is crucial for maintaining the database. Changes in one level doesn’t affectother level is data independence. There are three levels of database-1.Physical level2.Logical level3.View levelDatabase independence exits in physical and logical level.
Physical data independence indicates how really information is put away in a database. Changesmade in physical level don't affect the consistent level information.Logical data independence indicates how information is overseen inside a database. In the eventthat a few changes are done, it'll not influence information dwelling in the disk.[7] Data Redundancy IssuesData redundancy means multiple storing of same data over different locations. This increases thestorage unnecessarily. [8] Data integrity Data integrity in any database is the quality of data that maintains the accuracy and reliability. Itis important to maintain the accuracy throughout the entire life cycle because it is often used byorganization to make decisions.[9] Schema- It is the logical structure of the database. There are two types of schema-a. Physical schema- Database design at physical level.b. Logical schema- Database design at logical level.Field- A group of characters that has a specific meaningView- A stored query is called view.Index- It is a copy of selected data and rows that can be searched very efficiently and it isadditionally an immediate connection for the entire record. Data Dictionary- It is a crucial part of any database that contains the necessary records, dataownership and data relationships. Generally it contains the database metadata.
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