Consider the following MAILORDER relational schema describing the data for a mail order co...

Consider the following MAILORDER relational schema describing the data for a mail order company.

PARTS(Pno, Pname, Qoh, Price, Olevel)

CUSTOMERS(Cno, Cname, Street, Zip, Phone)

EMPLOYEES(Eno, Ename, Zip, Hdate)

ZIP_CODES(Zip, City)

ORDERS(Ono, Cno, Eno, Received, Shipped)

ODETAILS(Ono, Pno, Qty)

Qoh stands for quantity on hand : the other attribute names are self- explanatory. Specify and execute the following queries using the RA interpreter on the MAILORDER database schema.

a. Retrieve the names of parts that cost less than $20.00.

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b. Retrieve the names and cities of employees who have taken orders for parts costing more than $50.00.

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c. Retrieve the pairs of customer number values of customers who live in the same ZIP Code.

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d. Retrieve the names of customers who have ordered parts from employees living in Wichita.

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e. Retrieve the names of customers who have ordered parts costing less than $20.00.

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f. Retrieve the names of customers who have not placed an order.

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g. Retrieve the names of customers who have placed exactly two orders.