2. Database Management System (DBMS)

 2. Database Management System (DBMS)

 

Database

A database is an organized collection of related information that can be used for different purpose so that it can easily be accessed, managed, and updated.

E.g. Dictionary, Marks Ledger, Telephone Directory etc.

 

DBMS (Database Management System)
DBMS is a software which helps to extract, view and manipulate data in an organized way so that data can be accessed, managed and updated easily.
E.g.: MS-Access, Oracle, Fox pro, Dbase etc.
RDBMS (Relational Database Management System)
RDBMS is a database management system that is based on the relation model in which data is stored in the form of tables and the relationship among the data is also stored in the form of tables.
E.g.: SQL, MS-Access, Oracle, etc.

Importance / Advantages of DBMS  / Computerized database

a)     It controls data redundancy which means duplication of data.

b)     It allows sharing the existing data by different programs.

c)     Large volume of data can be stored and updated easily.

d)     It provides high security of data as well as maintains accurate database.

MS-Access

MS-Access is a relational database management system developed by Microsoft Corporation which is used to store and manipulates large volume of data in the form of table.

Features of MS-Access

a)     It provides the flexible ways to add, edit, delete and display the related data.

b)     Queries help to view, change and analyse the data indifferent ways.

c)     Forms are used for viewing and editing the information.

d)     Reports are used for summarizing and printing the data.

Objects of MS-Access

a) Table           b) Form    c) Query     d) Report
Computerized Database vs Non-Computerized Database

Computerized Database	Non-Computerized Database
It can store large volume of data. It is very fast to find a specific record.	It is limited by physical storage available.
The database can be kept secure by use of passwords.	The only security would be locking up the records.
We can search data very easily.	It can take a while to manually search through all of the records.
Data can be sorted into ascending or descending order on multiple criteria.	Difficult to sort data on more than one criteria.

Data
Data can be numbers, letters or symbols representing facts and figures which may or may not give any sense.
E.g.: Ram, student, 20, etc.

 

Information [SLC 2070]

Information is an organized collection of related data, which gives a complete sense.

 “Ram is a student. He is 20 years old.”, is information that gives a complete sense.

 

Define table.

Table is an object of Ms-Access that stores large volume of data in the form of rows and columns.
The different ways to create table are:
i) Design view
ii) Using wizard

iii) Entering data

Importance of table

a)     Different properties of a field can be set in a table.

b)     It provides options for primary key which helps to make data consistent.

Form

Form is an object of Ms-Access which provides graphical interface to enter data into the tables or multiple linked tables.

Methods to create a form are:
i) By using auto forms features.
ii) By using the form wizard features.
iii) By using your own in design view.

 

 

Importance / Function / Advantages of form

a)     It provides an interactive platform for input of data into the database.

b)     It helps to display data in more presentable form than a datasheet.

 

Query

Query is an object of Ms-Access which extracts and arranges information from a table in a manner that is specified.
The different types of query are:
i) Select query
ii) Action query
In action query, we have update query, append query, delete query and make-table query.

Advantages of query [SLC 2065]

a)     We can filter, perform calculations and summarize data.

b)     To perform mass update, delete or append new records to a table.

c)     To sort the records on the basis of one or more key fields.

Select query

A select query is the most common category and is used for extracting specific information from one or more tables in a database. It cannot make changes in tales.
Action query

Action query is a query which makes changes to many records in just one operation.

Update query

Update query is a type of action query which make global changes to a group of records in one or more tables.

 

Append query

The use of append query is to add a group of records at the end from one or more tables. It can do changes in tables by update, append.

 

Report

Report is an object of Ms-Access which displays the output in an effective way to present the data in a printed format.

The data sources for report are table and query.
The methods of creating report are:
i) Using design view
ii) Using report wizard

 

Why is Report created?

Report is created to print documents according to user’s specifications of the summarized information through query or table.

 

Importance of report

a)     It helps to prepare well formatted output by adding necessary titles, setting font colour or font size, etc..

b)     It presents the information retrieved through queries or tables.

 

Data type  

Data type is an attribute for a field that determines what type of data it can contain.

Any four data types of MS-Access are:
i) Text    ii) Number   iii) Memo   iv) Currency

 

 

 

 

While designing table structure which data types are suitable to store information about teacher’s name, address, salary and date of birth. [SLC 2065] [SLC 2068 S]
Teacher’s name - Text
Address – Text
Salary – Currency
Date of birth – Date/Time

Identify a record, field and value from the following table structure. [SQE 2074]

Roll        Name               Marks

1             Kopila                 87

2             Rabin Rana         56  

Ans: Record = 1  Kopila  87, 2     Prabin Rana    56

Field = Roll, Name, Marks

Value = 87, 56

 

List the field name from the following table structure.

Symbol No.	Name	Marks
00100200Q	Surya Gurung	85
00100201R	Birendra Sharma	91

 

 

What happens when we enter text in a numeric field?
Ans: If we enter text in a numeric field then it displays the errors.

Text

It is used for storing text or combination of text and numbers. It can store up to 255 characters. The default size of text field is 50.

Memo

It is used for storing lengthy text and numbers. It can store up to 65,535 characters.

Field properties

The four types of field properties of MS-Access are:
i) Caption                    ii) Format                    iii) Validation rule                 iv) Input mask

Input mask

Input mask is a field property that controls the value of a record and sets in a specific format.

Caption
Caption is a field property which displays an alternate name for the field to make the field name more explanatory. It can contain up to 2048 characters.

Validation rule:

A field property which enables to limit values that can be accepted into a field is known as validation rule.

Validation text

A field property which allows type text to be displayed if the user input value is prohibited by the validation rule is known as validation text.

Field size

Field size is a field property that specifies the maximum number of characters allowed in the field.

Format

The use of ‘Format’ field property is to display data in a different format.

 

 

 

 

Lookup Wizard

The use of Lookup Wizard is that it creates a field that allows choosing a value from another table or from a list of values by using a list box or combo box.

Hyperlink
The use of Hyperlink is that it stores hyper like addresses like email addresses, websites, database objects or other field.
Indexing

Indexing is one of the important properties of database that speed up searching and storing of records using on the field.

Relationship

Relationship is an association among several entities (table). Its types are:
i)One to one relationship
ii)One to many relationship
iii)Many to many relationship
Referential integrity
Referential integrity is a set of rules used by RDBMS to make sure that the relationships between tables are valid and that the related data is not accidentally changed or deleted.

Record [SEE 2075 S2]

Record is complete set of information. Record is a collection of multiple related fields in a row which gives complete information about a person or thing. E.g.: Ram Chabahil 4468790

Field [SEE 2075 S2]

Field is a small unit of information. A column in a table is called field, and it contains a specific piece of information within a record. E.g.: Name, Address, Telephone

Sorting [SEE 2073 U] [SLC 2068]
Sorting is the process of arranging the record in ascending or descending order according to a given field or fields. Sorted data is easier to handle than unsorted data. The advantages of sorting are:
i) It helps to find specific information quickly.
ii) It helps to arrange data in alphabetical order.

Filtering

Filtering is an option that selects the required records and displays the result.

Primary key

A key that uniquely identifies each record in a database is primary key. It is needed because it neither accepts duplicate values now null values.

Uses of Primary key [SLC 2069]
i) To reduce and control duplication of record in a table.
ii) To set the relationship between tables.

Composite key

The group of primary key that consists of two or more attributes is called composite key.

Foreign Key

Foreign key is a unique field or combination of fields in linked table whose value matches with a primary key in another table.

 

Data Redundancy [SEE 2074]

Data redundancy means repetition of same piece of data in a database in more than one location.. Data redundancy can be controlled in MS-Access by  normalization of database.