Test: ER-Model- 2 - Computer Science Engineering (CSE) MCQ

Many students can be enrolled in one or more courses and one course may have one or more students hence relation is many to many.

A foreign key is a key of a relation which is primary key of some other relation. A primary key is combined with foreign key then are ferential constraint is set up between the two relation, hence it creates a parent-child relationship between the tables that connects them.

Each employee has a unique id, name and salary, Employees may have different salary as per their category e.g. Manager, Engineer or Secretary.
Id is unique for each employee for a given employee with Id name is unique.
Hence, get Id and get name must be implemented in Superclass as whatever their designation it will not change. Get salary must be an abstract function in superclass and implemented in subclasses.

The given Relations R₁ and R₂ can be drawn as:

For relations R₁, and R₂, 3 tables are required as circled above.

Explanation: 3 minimum tables.

M, P are strong entities hence they must be represented by separate tables.

Many-to-one and one-to-many relationship sets that are total on the many-side can be represented by adding an extra attribute to the “many” side, containing the primary key of the “one” side. ( This way no extra table will be needed for Relationship sets )

M table is modified to include primary key of P side(i.e. P1). N is weak entity, and is modified to include primary key of P (i.e, P1).

Therefore there would be minimum of 3 tables with schema given below :
M ( M1, M2, M3, P1)
P ( P1, P2 )
N ( P1, N1, N2 )

The tables needed for the given ER-diagram are

which is covering aIl the attributes.

Since each table is to in 3^rd normal form for each multi-valued attribute individual table is to be created. Hence, total number of tables in the- database is 3.
1 for entity set E₁, 2 for entity set E₂ and 3 for attributes A₂₃.

The given expression can be understood as:

gives the name of female students who have less marks than other boys.
(ii) The expression  (student)) gives the name of all the female student from (i) and
(iii) The given expression finally calculates the names of female student who have marks more than all the boys in the class.

An entity is a “thing” or “object” in the real world that is distinguishable from all other objects.

Possible attributes of the instructor entity set are ID, name, dept name, and salary.