Question-5

Consider the relational schema given in tables below:

Order:

Order_id	User_id	Product_id	Quantity
…	…	…	…

Product:

Product_id	Product_name	Price
…	…	…

User:

User_id	User_name	Age	Gender
…	…	…	…

If the relations Order, Product, and Users have \(10\), \(6\), \(8\) rows respectively, what is the maximum number of rows returned by the following query?

(Note: Consider all the attributes have NOT NULL constraint.)

SELECT * FROM Orders RIGHT OUTER JOIN Users ON Orders.user_id = Users.user_id;

Answer

\(17\)

Solution

In the Users table, the \(user\_id\) is the primary key, so all values should be unique. The maximum number of rows returned by the given query occurs when all values of \(user\_id\) in the Orders table are the same. The maximum number of rows returned by the given query is \(10 + 7 = 17\).