This section asks you to write some queries in Relational Algebra and SQL.Your SQL queries will be graded by running them in MySQL on test cases; queries that return the wrong answer will receive 0 points, i.e. there is no partial credit. In particular, please make sure your query returns the right column(s).

Consider the schema given by the following two SQLCREATEstatements.

  CREATE TABLE SuppInfo (suppid INTEGER NOT NULL,
  

  prodid INTEGER NOT NULL,
  

  PRIMARY KEY (suppid, prodid));
  

  

  CREATE TABLE Purchases (purchaseid INTEGER PRIMARY KEY,
  

  custid INTEGER,
  

  prodid INTEGER,
  

  purchasemethod INTEGER);
 

This schema comes from a simple retail setting. The rst table keeps track of which suppliers supply which products, and each (sno, pno) pair states that supplier number sno suppliers product number pno. The second table keeps track of customer purchases { a purchase has an ID, a customer ID and a ag to specify whether the purchase was in person, online or over the phone. Write the following queries over the above schema.For the SQL portion, each of your answers must be a single SQL query.

(a) Find all the pairs of suppids for suppliers that supply the exact same products. Each pair of suppids should appear only once in the answer. Give queries in relational algebra (4 points) and SQL (4 points).
(b) Find custids of all customers who made purchases usingexactly two dierent methods. E.g. if a customer made three purchases { one over the phone and two in person, their record is included in the answer. But if they made two purchases, both online, their record is not included. Give queries in relational algebra (4 points), SQL using GROUP BY(4 points) and SQL without using GROUP BY(4 points).

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