DBMSNotes

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DATABASE MANAGEMENT SYSTEM

A Database is a well defined collection of data. A Database Management

System (DBMS) is a set ofcomputer programs that controls the creation, maintenance,

and the use of the database in a computer platform or of an organization and its end users.

It allows organizations to place control of organization-wide database development in the

hands ofdatabase administrators (DBAs) and other specialists. A DBMS is a system

software package that helps the use of integrated collection of data records and files

known as databases. It allows different user application programs to easily access the

same database. DBMSs may use any of a variety ofdatabase models, such as the network

model orrelational model.

In large systems, a DBMS allows users and other software to store and retrieve

data in a structured way. Instead of having to write computer programs to extract

information, user can ask simple questions in a query language. Thus, many DBMS

packages provide Fourth-generation programming language (4GLs) and other application

development features. It helps to specify the logical organization for a database and

access and use the information within a database. It provides facilities for controlling data

access, enforcing data integrity, managing concurrency controlled, and restoring

database.

DATABASE well defined collection of data

MANAGEMENT

SYSTEM software

In short, DBMS is a SOFTWARE that performs the MANAGEMENT operations

(SELECT, DELETE, INSERT and UPDATE) on a well defined collection of data.

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SELECT

UPDATE

DELETE

INSERT

DBMS
http://en.wikipedia.org/wiki/Computer_programhttp://en.wikipedia.org/wiki/Databasehttp://en.wikipedia.org/wiki/End_userhttp://en.wikipedia.org/wiki/Database_administratorhttp://en.wikipedia.org/wiki/Database_administratorhttp://en.wikipedia.org/wiki/Database_modelhttp://en.wikipedia.org/wiki/Network_modelhttp://en.wikipedia.org/wiki/Network_modelhttp://en.wikipedia.org/wiki/Relational_modelhttp://en.wikipedia.org/wiki/Data_structurehttp://en.wikipedia.org/wiki/Query_languagehttp://en.wikipedia.org/wiki/Fourth-generation_programming_languagehttp://en.wikipedia.org/wiki/Data_accesshttp://en.wikipedia.org/wiki/Data_accesshttp://en.wikipedia.org/wiki/Data_integrityhttp://en.wikipedia.org/wiki/Computer_programhttp://en.wikipedia.org/wiki/Databasehttp://en.wikipedia.org/wiki/End_userhttp://en.wikipedia.org/wiki/Database_administratorhttp://en.wikipedia.org/wiki/Database_modelhttp://en.wikipedia.org/wiki/Network_modelhttp://en.wikipedia.org/wiki/Network_modelhttp://en.wikipedia.org/wiki/Relational_modelhttp://en.wikipedia.org/wiki/Data_structurehttp://en.wikipedia.org/wiki/Query_languagehttp://en.wikipedia.org/wiki/Fourth-generation_programming_languagehttp://en.wikipedia.org/wiki/Data_accesshttp://en.wikipedia.org/wiki/Data_accesshttp://en.wikipedia.org/wiki/Data_integrity

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EXAPMLE FOR A BATABASE AND THE OPERATIONS

Let MANAGEMENTSTUDIES be the database. A database can have any number of

files in it. So ourMANAGEMENTSTUDIES database has three files namely

1. student

2. teachingstaff

3. nonteachingstaff

Let us consider only the student file now. The files in the database are arranged in the

form of a table containing row and columns and the data will be arranged in these rows

and columns.

The student database file will look like this:

Roll. No Name Age AttendancePercent MarkPercent

1 Anish 20 70 70

2 Eby 21 80 80

3 Archana 20 90 90

4 Dhanya 20 78 80

5 Chinchu 20 90 80

6 Feby 23 80 70

7 Jain 26 50 50

8 Meenu 23 70 89

9 Arun 23 60 68

10 Robin 22 90 85

Now let us see how we can perform the Management operations on the above database

file:

2

student

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1. Retrieval or Selection from the database file:

The selection or retrieval from a database is possible with the help of the SELECT

command. Its syntax is as follows:

Example:-

SELECT Roll. No, Name, Age

FROM student

WHERE MarkPercent>80

Result:

Roll. No Name Age

2 Eby 21

3 Archana 20

4 Dhanya 20

5 Chinchu 20

8 Meenu 23

10 Robin 22

2. Inserting a new data into the student database file

3

SELECT

FROM name of the database file

WHERE condition

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The insertion into a database file is possible with the help of the INSERT command.

Its syntax is as follows:

Example:-

INSERT INTO student (Roll. No, Name, Age, AttendancePercent, MarkPercent)

VALUES (11, Subin, 23, 79, 60)

Result:


1 Anish 20 70 70

2 Eby 21 80 80

3 Archana 20 90 90

4 Dhanya 20 78 80

5 Chinchu 20 90 80

6 Feby 23 80 70

7 Jain 26 50 50

8 Meenu 23 70 89

9 Arun 23 60 68

10 Robin 22 90 85

11 Subin 23 79 60

3. Updating data in the student database file

4

INSERT INTO name of the database file (fields to be inserted)

VALUES (values to be given for the field we are inserting)

student

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Updating a database is possible with the help of the SELECT command. Its syntax is

as follows:

Example:-

UPDATE student

UPDATE student

SET AttendancePercent =90

WHERE MarkPercent>80

Result:


2 Eby 21 90 80

3 Archana 20 90 90

4 Dhanya 20

90

80

5 Chinchu 20

90

80

8 Meenu 23

90

89

10 Robin 22

90

85

4. Deleting data from the student database file

The deletion from a database is possible with the help of the DELETE command. Its

syntax is as follows:

5

UPDATE name of the database file

SET write the updation that is to be made on the existing database file

WHERE condition

student

DELETE

FROM database file name

WHERE condition

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Example:-

DELETE FROM student

WHERE Roll. No = 5

Result:


1 Anish 20 70 70

2 Eby 21 80 80

3 Archana 20 90 90

4 Dhanya 20 78 80

6 Feby 23 80 70

7 Jain 26 50 50

8 Meenu 23 70 89

9 Arun 23 60 68

10 Robin 22 90 85

11 Subin 23 79 60

6

student

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DDL

Data Definition Language (DDL) statements are used to define the database structure or

schema. Some examples:

o CREATE - to create objects in the database

o ALTER - alters the structure of the database

o DROP - delete objects from the database

DML

Data Manipulation Language (DML) statements are used for managing data within

schema objects. Some examples:

o SELECT - retrieve data from the a database

o INSERT - insert data into a table

o UPDATE - updates existing data within a table

o DELETE - deletes all records from a table, the space for the records remain

TCL

Transaction Control (TCL) statements are used to manage the changes made by DML

statements. It allows statements to be grouped together into logical transactions.

o COMMIT - save work done

o ROLLBACK - restore database to original since the last COMMIT

A spreadsheet is a computer application that simulates a paper, accounting

worksheet. It displays multiple cells that together make up a grid consisting of rows and

columns, each cell containing alphanumeric text, numeric values or formulas. A formula

defines how the content of that cell is to be calculated from the contents of any other cell

(or combination of cells) each time any cell is updated. Spreadsheets are frequently used

for financial information because of their ability to re-calculate the entire sheet

automatically after a change to a single cell is made.

A Sample Spreadsheet

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http://en.wikipedia.org/wiki/Computer_applicationhttp://en.wikipedia.org/wiki/Worksheethttp://en.wikipedia.org/wiki/Worksheethttp://en.wikipedia.org/wiki/Alphanumerichttp://en.wikipedia.org/wiki/Formulahttp://en.wikipedia.org/wiki/Financialhttp://en.wikipedia.org/wiki/Computer_applicationhttp://en.wikipedia.org/wiki/Worksheethttp://en.wikipedia.org/wiki/Alphanumerichttp://en.wikipedia.org/wiki/Formulahttp://en.wikipedia.org/wiki/Financial

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