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Consider the relational schema given below, where eId of the relation dependent is a foreign key referring to empId of the relation employee. Assume that every employee has at least one associated dependent in the dependent relation. Employee (empId, empName, empAge) Dependent(depId, eId, depName, depAge) Consider the following relational algebra query: ΠempId(employee)-ΠempId (employee⋈(empId = eID)∧(empAge ≤ depAge)dependent) The above query evaluates to the set of empIds of employees whose age is greater than that of

Consider the relational schema given below, where eId of the relation dependent is a foreign key referring to empId of the relation employee. Assume that every employee has at least one associated dependent in the dependent relation. Employee (empId, empName, empAge) Dependent(depId, eId, depName, depAge) Consider the following relational algebra query: ΠempId(employee)-ΠempId (employee⋈(empId = eID)∧(empAge ≤ depAge)dependent) The above query evaluates to the set of empIds of employees whose age is greater than that of Correct Answer all of his/her dependents

Explanation:

Example:

Employee Relation:

EmpID

empName

empAge

e1

A

20

e2

B

25

e3

C

24

 

Dependent Relation:

depID

eID

depName

Age

d1

e1

X

30

d2

e1

Y

25

d3

e1

Z

20

d4

e2

P

18

d5

e2

P

17

d7

e3

Z

35

 

R1=ΠempId (employee⋈(empId = eID)∧(empAge ≤ depAge)dependent)

Output : e1,e3

R2=ΠempId(employee)

Output: e1,e2,e3

R = R2 - R1= {e1,e2,e3} - {e1,e3} = e2

  • e2 is output that is saying that set of empIds of employees whose age is greater than that of all of his/her dependents.

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