Explain on how to solve the following Relational algebra(NOT SQL). 

 

A construction company works with a database that stores information about contractors, materials, and sites. The Consignment relation records instances of a contractor delivering materials for a construction site.

The schema for the database used in this question is as follows: (note that primary keys are shown underlined, foreign keys in bold). 

 

 

Contractor (C-ID, Name, phone, Address)

 Material (M-ID, MaterialName, Type, Weight, Grade)

 Site (Site-ID, Name, StartYear, Address) 

Consignment (C-ID, M-ID, Site-ID, Quantity, Datestart, DateEnd) 

 

 

 

1. Find the name of any Contractor who have delivered materials to the site called "Humpty Doo Place" or to the site called "Noonamah Place".

 

 2. Find the name of any Contractor who have delivered materials to the site called "Humpty Doo Place" and to the site called "Noonamah Place". 

 

3. List the names of Contractors who have delivered the material called "Precious Bamboo". 

 

4. Find the names of sites that have had materials delivered by "Move Forward Transport" or a contractor located in Wagga Wagga. 

 

5. List the details of any Contractor who has delivered materials to a site that stared in 2023 and (the site is) located in Alice Springs.

 

 6. Find the name of any material that was not used on a site that commenced in 2022.

 

 7. List the name of any material that has been delivered to all sites that commenced in 2023.