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Basics of Database management system

Basics of the Database management system

I this article we will learn about:

 ■ Purpose of Database Systems

 ■ View of Data

 ■ Data Models 

■ Data Definition Language

 ■ Data Manipulation Language

 ■ Transaction Management

 ■ Storage Management

 ■ Database Administrator 

■ Database Users 


Database Management System:(DBMS)

■ Collection of interrelated data 

■ Set of programs to access the data

■ DBMS contains information about a particular enterprise 

■ DBMS provides an environment that is both convenient and efficient to use. 

■ Database Applications: 

★ Banking: all transactions 

★ Airlines: reservations, schedules 

★ Universities: registration, grades 

★ Sales: customers, products, purchases 

★ Manufacturing: production, inventory, orders, supply chain 

★ Human resources: employee records, salaries, tax deductions 

■ Databases touch all aspects of our life


Reason for Database System 


■ In the good 'ole days, information base applications were based on top of 

record frameworks 

■ Drawbacks of utilizing record frameworks to store information: 

★ Data repetition and irregularity 

✔ Multiple record designs, duplication of data in various documents 

★ Difficulty in getting to information 

✔ Need to work on another program to complete each new undertaking 

★ Data seclusion — various documents and configurations 

★ Integrity issues 

✔ Integrity imperatives (for example account balance > 0) become part 

of program code 

✔ Hard to add new limitations or change existing one 

Levels of Abstraction Levels of Abstraction 

■ Physical level depicts how a record (e.g., client) is put away. 

■ Logical level: depicts information put away in the data set, and the 

connections among the information. 

type client = record 

name: string; 

road: string; 

city: number; 

end; 

■ View level: application programs conceal subtleties of information types. 

Perspectives can likewise shroud data (e.g., pay) for security 

purposes.

Instances and Schemas 


■ Similar to types and factors in programming dialects 

■ Schema – the intelligent design of the information base 

★ e.g., the data set comprises data about a bunch of clients and 

accounts and the connection between them) 

★ Analogous to type data of a variable in a program 

★ Physical pattern: data set plan at the actual level 

★ Logical pattern: data set plan at the legitimate level 

■ Instance – the real substance of the information base at a specific point on the schedule 

★ Analogous to the worth of a variable 

■ Physical Data Independence – the capacity to change the actual pattern 

without changing the intelligent pattern 

★ Applications rely upon the sensible outline 

★ by and large, the interfaces between the different levels and segments ought to 

be obvious so that adjustments of certain parts don't genuinely impact others. 

Information Models Data Models 


■ An assortment of devices for depicting 

★ information 

★ information connections 

★ information semantics 

★ information imperatives 

■ Entity-Relationship model 

■ Relational model 

■ Other models: 

★ object-situated model 

★ semi-organized information models 

★ Older models: network model and progressive model 

Substance Relationship Model Entity-Relationship Model 

Illustration of outline in the substance relationship model 


Information Definition Language (DDL) Data Definition Language (DDL) 


■ Specification documentation for characterizing the data set composition 

★ E.g. 

make table record ( 

account-number char(10), 

balance whole number) 

■ DDL compiler creates a bunch of tables put away in an information 

word reference 

■ Data word reference contains metadata (i.e., information about information) 

★ data set composition 

★ Data stockpiling and definition language 

✔ language in which the capacity design and access techniques 

utilized by the information base framework are determined 

✔ Usually an augmentation of the information definition language 

SQL 


■ SQL: broadly utilized non-procedural language 

★ E.g. discover the name of the client with client id 192-83-7465 

select customer.customer-name 

from client 

where customer.customer-id = '192-83-7465' 

★ E.g. discover the equilibriums of all records held by the client with 

client id 192-83-7465 

select account.balance 

from the contributor, account 

where depositor.customer-id = '192-83-7465' and 

depositor.account-number = account.account-number 

■ Application programs by and large access information bases through one of 

★ Language augmentations to permit inserted SQL 

★ Application program interface (for example ODBC/JDBC) which permit SQL 

questions to be shipped off a data set 

Administrator Database Administrator 


■ Coordinates every one of the exercises of the information base framework; the 

information base manager has a decent comprehension of the 

venture's data assets and requirements. 

■ Database director's obligations include: 

★ Schema definition 

★ Storage design and access strategy definition 

★ Schema and actual association change 

★ Granting client position to get to the data set 

★ Specifying uprightness imperatives 

★ Acting as contact with clients 

★ Monitoring execution and reacting to changes in 

necessities 

Capacity Management Storage Management 


■ Storage supervisor is a program module that gives the 

the interface between the low-level information put away in the data set and 

the application projects and inquiries submitted to the framework. 

■ The capacity supervisor is mindful of the accompanying undertakings: 

★ communication with the document director 

★ effective putting away, recovering, and refreshing of information
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