Reference no: EM13509190

1.Explain the statement that relational algebra operators can be com-posed. Why is the ability to compose operators important?

2.Consider the Supplier-Parts-Catalog schema from the previous ques-tion. State what the following queries compute:

1. πsname(πsid((σcolor=red_Parts) ;: (σcost<100Catalog)) ;: Suppliers )

2. πsname(πsid((σcolor=red_Parts) ;: (σcost<100Catalog) ;: Suppliers ))

3. (πsname((σcolor=red_Parts) ;: (σcost<100Catalog) ;: Suppliers )) ∩

(πsname((σcolor=green_ Parts) ;: (σcost<100Catalog) ;: Suppliers ))

4. (πsid((σcolor=red_Parts) ;: (σcost<100Catalog) ;: Suppliers )) ∩

(πsid((σcolor=green_ Parts) ;: (σcost<100Catalog) ;: Suppliers ))

5. πsname((πsid,sname((σcolor=red_Parts) ;: (σcost<100Catalog) ;: Suppliers )) ∩

(πsid,sname((σcolor=green_ Parts) ;: (σcost<100Catalog) ;: Suppliers )))