City Guilds Model Questions Vol1 2023 Information Technology Question 17
Practice objective / multiple choice question 17 from the 2023 City Guilds Model Questions Vol1 Information Technology examination.
Consider the relational schema: - Employees(EmpID, DeptID, Salary) - 500 rows - Departments(DeptID, ManagerID) - 20 rows - Projects(ProjID, DeptID) - 80 rows - WorksOn(EmpID, ProjID, Hours) - 1500 rows Selectivity of the condition Salary > 50000 on Employees is 0.2 and selectivity of Hours > 10 on WorksOn is 0.3. Write a relational‑algebra expression that returns the EmpID of employees who (i) have Salary > 50000, (ii) work on a project where Hours > 10, and (iii) the project belongs to the same department as the employee. Estimate the number of resulting rows assuming a join order that minimises intermediate result sizes.
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This is City Guilds Model Questions Vol1 2023 Information Technology Question 17. It is one of the objective questions from the 2023 City Guilds Model Questions Vol1 Information Technology examination.
Difficulty level: Medium .
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