Product(pid, name, type, manufacturer, price), Buys(cid, pid), Customer(cid, cname, age, gender) a) Write the following query in relational algebra. Find the names of all customers who have purchased all products manufactured by Sears. b) Write the following query in SQL. Find the names of all customers who have not purchased the most expensive product c) Write the following query in SQL. Find the names and cids of all customers who have purchased the second most expensive product. You can assume that no two products have the same prices.
SQL
SQL stands for Structured Query Language, is a form of communication that uses queries structured in a specific format to store, manage & retrieve data from a relational database.
Queries
A query is a type of computer programming language that is used to retrieve data from a database. Databases are useful in a variety of ways. They enable the retrieval of records or parts of records, as well as the performance of various calculations prior to displaying the results. A search query is one type of query that many people perform several times per day. A search query is executed every time you use a search engine to find something. When you press the Enter key, the keywords are sent to the search engine, where they are processed by an algorithm that retrieves related results from the search index. Your query's results are displayed on a search engine results page, or SER.
Consider the following schema (keys are in Bold):
Product(pid, name, type, manufacturer, price), Buys(cid, pid), Customer(cid, cname, age, gender)
a) Write the following query in relational algebra. Find the names of all customers who have purchased all products manufactured by Sears.
b) Write the following query in SQL. Find the names of all customers who have not purchased the most expensive product
c) Write the following query in SQL. Find the names and cids of all customers who have purchased the second most expensive product. You can assume that no two products have the same prices.
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