distribution of marks for second semester internal sessional evaluation external evaluation...
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Distribution of MarksFor
Second SemesterInternal Sessional Evaluation Externa
l Evaluati
onAssignm
ent/Project
Quizzes
Class Attenda
nce
Mid-Term Test
Total Sessio
nal
Terminal Exam
Final Evaluati
on
10 10 5 25 50 50 100
By ILTAF MEHDI (MCS, MCSE, CCNA) An introduction to Relational Database
1
Remember:
Chapter No
Chapter NamePage No
1.Database Foundation OR An Overview of Database Management System (DBMS)
2. Semantic Modeling OR Entity Relationship Model (ERD)
3. An introduction to Relational Database
4. Normalization
5. Relational Algebra
6. An Introduction to Structured Query Language (SQL)
By ILTAF MEHDI (MCS, MCSE, CCNA) An introduction to Relational Database
2
Course Contents
COURSE INSTRUCTOR:
ILTAF MEHDI
By ILTAF MEHDI (MCS, MCSE, CCNA) An introduction to Relational Database
3
Ch
ap
ter
No:
03
Ch
ap
ter
No:
03
Def:“A data model is a representation of data about entities, events, activities and their relationship”.
A data model represents an organization itself. The purpose of data model two-fold: First “to
represent data” and second “to be understandable”.
If a data model accurately and completely represent required data and is understandable then it can be used in some application.
By ILTAF MEHDI (MCS, MCSE, CCNA) An introduction to Relational Database
4
There are basically three types of data model:
1)Hierarchical Data Model2)Network Data model3)Relational Data model
By ILTAF MEHDI (MCS, MCSE, CCNA) An introduction to Relational Database
5
1) Relational Data Model: It also called Relational Database Model. The Relational Data Model is the most
recent and best of the three database models.
It was developed by C.F Codd in 1970. This model represents database as a set of
normalized relations. “In Relational Model data are represented in
the form of tables with rows and columns”.
By ILTAF MEHDI (MCS, MCSE, CCNA) An introduction to Relational Database
6
Deptt-No
Deptt-Name
Deptt-Location
D100 IT West
D101 Management
East
D102 English South
By ILTAF MEHDI (MCS, MCSE, CCNA) An introduction to Relational Database
7
Emp-No
Emp-Name
Emp-Phone #
Deptt-No
E10 Mehdi 336 D100
E11 Danish 448 D101
E12 Nasir 500 D102
DEPARTMENT
EMPLOYEE
Relational Database Model
Notice that there is no physical data structure representing relationship between two tables (relations). Instead relationships are represented logically by the values that are stored within table’s columns.For example: In above figure, the Department-Number (Deptt-No) for each Employee is stored in Employee table.
The above tables have the following properties:1. Each column contained values about some
attribute.2. Each column has distinct name.3. Each row of a table must be unique, means,
that no two rows have the identical data.4. Each row in the relation is called TUPLE.5. Each column in the relation is called DOMAIN.
By ILTAF MEHDI (MCS, MCSE, CCNA) An introduction to Relational Database
8
6. Record: “The combination of more than one fields about a
single entity is called record of that entity”.For example: The record of STUDENT may have fields Roll-No,
Name, Father Name, Gender, Address, Program and Marks. Then this combination of fields is called the record of a particular STUDENT.
By ILTAF MEHDI (MCS, MCSE, CCNA) An introduction to Relational Database
9
Roll-No
Name F-Name
Gender
Address
Program
Marks
100 Abdullah
Zain Male Kabul BCS 40
101 Spogmay
Iqbal Female
Kabul BCS 47
1st RECORD
2nd RECORD
FIELDSFIELDS
STUDENT FILE
7. File or Data File: “The collection of more than one related records
is called a file or data file”. All the records of the should be of the same type. In the above File, two logical records about
STUDENT are shown.8. Degree of file: “The total number of the columns in a file is
called Degree of a file”.9. Cardinality: The total number of rows or records in a file is
called cardinality.
By ILTAF MEHDI (MCS, MCSE, CCNA) An introduction to Relational Database
10
By ILTAF MEHDI (MCS, MCSE, CCNA) An introduction to Relational Database
11
Roll-No
Name F-Name
Gender
Address
Program
Marks
100 Abdullah
Zain Male Kabul BCS 40
101 Spogmay
Iqbal Female
Kabul BCS 47
Two Records
SEVEN FIELDSSEVEN FIELDS
Degree of File: 07Degree of File: 07
Cardinality: 02Cardinality: 02
STUDENT Relation
Properties of Relation
The Relational Data Model has several advantages but some of them are given below:
1)Implementation Independence: R.D.M logically represents all relationship
implicitly and completely.2)Terminology: The R.D.M has developed with its own set of
terminology.3)Logical Key Pointer: The R.D.M uses primary and secondary keys
to represent relationship between two relations.
By ILTAF MEHDI (MCS, MCSE, CCNA) An introduction to Relational Database
12
Def: “a key is a data item which is used to identify a record or relation”.
OR An attribute through which we can
access an entity within entity class”.
By ILTAF MEHDI (MCS, MCSE, CCNA) An introduction to Relational Database
13
There are different types of keys which are given below:
1. Super Key2. Candidate Key3. Primary Key4. Atomic Key5. Concatenated Key 6. Compound Key7. Secondary Key8. Foreign Key
By ILTAF MEHDI (MCS, MCSE, CCNA) An introduction to Relational Database
14
1) Super Key:“An attribute or combination of attributes that
can uniquely identify an entity is called super key”.
For Example: consider the STUDENT relation;STUDENT (st-no, st-name, st-age, st-gender etc) A super key may contain some extra
attributes that are not necessary to uniquely identify an entity.
i.e. { st-no, st-name, st-age } In-fact a super key can be:{ Primary-key + Non-key attribute }
By ILTAF MEHDI (MCS, MCSE, CCNA) An introduction to Relational Database
15
2) Candidate Key: “An attribute or combination of attributes
that uniquely identifies each instances of an entity is called Candidate Key”.
For Example: consider the EMPLOYEE relation;
EMPLOYEE (NIC-No, Name, Address etc) Here NIC-No and Name is a super key that
contain extra attributes that is not necessary for unique identification. So it is not a candidate key. But NIC-No is a Candidate Key.
An entity may be uniquely identified by more than one candidate keys.
By ILTAF MEHDI (MCS, MCSE, CCNA) An introduction to Relational Database
16
3) Primary Key: Def: “A primary key is a key that have been
selected as an identifier for an entity type”. It is also called identifier.For example: Consider the EMPLOYEE relation;EMPLOYEE (Emp-No, Emp-Name, Emp-
Address) If we select Emp-No as an identifier then it
is Primary Key.
By ILTAF MEHDI (MCS, MCSE, CCNA) An introduction to Relational Database
17
4) Atomic Key: Def: “A Primary Key is called atomic key or
simple key when it consists of a single attribute to identify a record or relation”.
For Example: Consider the STUDENT relation;
STUDENT (St-ID, St-Name, St-F/Name,St-Address)
St-ID is atomic key for the STUDENT relation
By ILTAF MEHDI (MCS, MCSE, CCNA) An introduction to Relational Database
18
5) Concatenated Key: Def: “The combination of two or more keys to
uniquely identify a record is called Concatenated Key”.
For Example: Consider the STUDENT relation;STUDENT (class-no, name, address, class)
“We have student file of Computer Science Department that contain information about Previous and Final students”. In this case class-no can’t uniquely identify a student because there may be duplication of students for class i.e. Previous and Final. So both class-no and class can be used as Primary Key in this case. Such a key is called Concatenated Key.
By ILTAF MEHDI (MCS, MCSE, CCNA) An introduction to Relational Database
19
6) Compound Key: Def: “A Compound Key is a Primary Key that
consists of more than one attribute and every attribute in the key is Primary key in some other relation”.
For Example: Consider the relation;ORDER-LINE (order-no, product-no,
quantity, date) So the primary key consists of order-no and
product-no. But order-no is primary key in ORDER relation and product-no is primary key in PRODUCT relation. So it is a Compound Key.
By ILTAF MEHDI (MCS, MCSE, CCNA) An introduction to Relational Database
20
7) Secondary Key: “A secondary key is a data item that does
not uniquely identify a record but identifies a number of records in a set that share some common property ”.
For Example: Name, Address, Age etc are the examples of Secondary Key.
Now consider the Query:
So based on secondary key “Age” this query will select all students whose age is 20.
By ILTAF MEHDI (MCS, MCSE, CCNA) An introduction to Relational Database
21
Select * from student where Age=‘20’ ;
Select * from student where Age=‘20’ ;
8) Foreign Key: Def: “An attribute that appear as non-
key in one relation but primary key in another relation is called Foreign Key”.
For Example: Consider the relations;DEPARTMENT (Deptt-No, Deptt-Name,
Location)TEACHER (T-No, T-Name, Deptt-No ) Here Deptt-No is a foreign key because it
act as primary key in DEPARTMENT and as non-key attribute in TEACHER relation.
By ILTAF MEHDI (MCS, MCSE, CCNA) An introduction to Relational Database
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