Question

Consider the following database instance, which contains information about employees and the projects to which they are assigned:

Employee

empId	lastName
E101	Smith
E105	Jones
E110	Adams
E115	Smith

Project

projectNo	projectName	budget
P10	Hudson	50000
P15	Columbia	60000
P20	Wabash	40000
P23	Arkansas	80000

Assign

employeeId	projectNo	hours
E101	P10	40
E101	P15	30
E104	P10	20
E110	P15	30
E110	P20	30
E115	P10	20
E115	P20	30

• Show the table that would be produced by each of the following relational algebra commands:

A. SELECT Employee WHERE lastName = ‘Adams’

B. SELECT Project WHERE budget < 70000 GIVING CheapProj
PROJECT ChapProj OVER projectName

C. SELECT Assign WHERE hours > 25 GIVING MuchWork
PROJECT MuchWork OVER employeeId

Answer 1

Solution

A. SELECT Employee WHERE lastName = ‘Adams’

empId	lastName
E110	Adams

B. SELECT Project WHERE budget < 70000 GIVING CheapProj
PROJECT ChapProj OVER projectName

projectNo	projectName	budget
P10	Hudson	50000
P15	Columbia	60000
P20	Wabash	40000

C. SELECT Assign WHERE hours > 25 GIVING MuchWork
PROJECT MuchWork OVER employeeId

employeeId	projectNo	hours
E101	P10	40
E101	P15	30
E110	P15	30
E110	P20	30
E115	P20	30

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All the best