Post on 24-Jan-2017
HI, EVERYBODY!!
GROUP MEMBERSSERIAL NO.
NAME ID
1 SIFAT ARA SABA 21-1032 TANIA AKTAR 21-1183 KEYA DATTA 21-1244 AEYSHA AKTER RANI 21-1585 MD. IMTIAJ HOSSAIN 21-0976 MD. RAKIBUL ISLAM 21-0737 MD. SHAKIL AHMED 21-1068 RUHUL AMIN 21-1339 MD. PAPPU MIAH 21-17810 MD. SAYED MURSALIN 21-013
ER DIAGRAM An entity relationship diagram
shows the relationship of entity sets stored in a database. At first glance an entity relationship diagram looks like a flowchart.
An entity relationship diagram for a college database
Now we are going to design an ER diagram for a college database. At first we have to discuss the database of a college that is normally seen...
1. A college contains many departments.
2. Each department has a number of sections.
3. Each department can offer any number of courses.
An entity relationship diagram for a college database
4. Many instructor work in a department.5. An instructor can work only in one
department. 6. An instructor can be head of his concerned
department. 7. An instructor teaches any number of
courses. 8. Each course is taught by only one instructor.9. Each student is enlisted in only one section.10. Each course can have any number of
students.
ER DIAGRAM Now we have to follow the 4 step procedures to
construct the ER diagram for the above database..
1. Identify the entities and relationship..
Here the entities are- Department Section Courses Instructors students
THE RELATIONSHIP
Department Has sections
Department Has Courses
Department Has Instractor
Students Enroll Courses
Instractor Teaches Course
2. Integrate the entities and relationships
DEPT. HAS SECTIONINST
RUCTED BY
HAS
OFFER
COURSE
TAUGHTBY
INSTRUCTOR
ENROLLED BY
STUDENTS
M
1
1
N
M
NM
M
M
M
M
1
1. A department has many sections and each department can have many sections, so the cardinality between dept. and sections is many to many. (M:N)
2. One dept offer many courses but one particular course can be offered by only one department and courses. So the cardinality between dept and courses is one to many. (1:N)
3. A department has many instructor but one instructor can be a member of only one department. So the cardinality between department and instructor is one to many. (1:N)
3. Assign Cardinalities between the relationships:
4.One course can b enrolled by many students and one student can enrolled for may courses. Hence the cardinality between students and courses is many to many. (M:N)
5. One course is taught by only one instructor but one instructor teaches many courses. Hence the cardinality between courses and instructor is many to one.(N:1)
4. Specify the data attributes:
Department: name, location Ccourse: course name, course code,
duration Instructor: ID, name, Phone number,
Designation. Student: ID, name, phone number Section: A, B, C
DEPT
OFFER
COURSE
ENROLLEDBYSTUDENTS
HAS
INSTRACTOR
HAS
SECTION
TAUGHTBY
Name
Location
Dutrion
Code
Name
Phone
Name
Id
Designation
Phone
Name
Id BA
Now the complete diagram is