Retrieve the following information by using a series of relational algebraic operations and also by using relational calculus statement:

Question

Use tables given in fig. 1-2. The relational database notation of
tables is given below:

a. All employee names.
b. All employees working in department number 20.
c. All employees who are making $50,000 or more.
d. All employees who are working in department 20 and also making more
than $25,000.
e. Vendor who supplied parts for the project in Miami during the year
2000.

Answer 1

a. All employee names.

A = EMPLOYEE (Ename)

(r.Ename) : r in EMPLOYEE

b. All employees working in department number 20.
B = Sel (EMPLOYEE : DeptNo = 20)
C = B (Ename)

(r.Ename) : r in EMPLOYEE and r.DeptNo = 20

c. All employees who are making $50,000 or more.
D = Sel (EMPLOYEE : Salary >= 50000)
E = D (Ename, Salary, DeptNo)

(r.Ename, r.Salary, r.DeptNo) : r in EMPLOYEE
and r.Salary >= 50000

d. All employees who are working in department 20 and also making more
than $25,000.

F = Sel (EMPLOYEE : DeptNo = 20 and Salary > 25000)
G = F (Ename, Salary)

(r.Ename, E.Salary) : r in EMPLOYEEand r.DeptNo = 20

and r.Salary > 25000

e. Vendor who supplied parts for the project in Miami during the year
2000.

H = Sel (PROJ2000 : Loc = ‘Miami’)
I = join (H, PRJPARTS : ProjNo = ProjNo)
J = join (I, PARTS : PartNo = PartNo)
K = J (Vendor)

(c.Vendor) : a in PROJ2000 AND b in PRTPARTS

and c in PARTS
and a.ProjNo = b.ProjNo
and b.PartNo = c.PartNo