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2.3 Given the relations R (A, B) and S (B, C) where values are all integers. Examine the undermentioned three relational algebra expressions: a. A, C(R⋈B=1S) b. A(B = 1R)XC(B = 1S) c. A, C (ARXB = 1S) Two of the three expressions are equivalent (i.e., they produce the same answer on all databases), while one of them can produce a different answer.

2.3.1 Which query can produce a contrasting answer? Give the simplest database instance you can think of where a different answer is produced. (5)

2.3.2 Why do we care that the expressions are equivalent? (5)

2.3.3 How can we determine that the expressions are equivalent?

2.1 Assuming the following relations from a customer database, write relational algebra expression for each statement using symbolic notations. Customer (cid, cname, rating, salary) Item (iid, iname, type) Order (cid, iid, day, qty)

2.1.1 Find the names of customers who have ordered item with id 087. (2)

2.1.2 Find the names of customers who have ordered a television i.e., an item of type television. 

2.2 Use information on MYSQL student_reg table to login making sure you are using proper credentials.

2.3 Register button should take the user to a new page that allows them to register if they are not registered in the system.

2.4 If student’s credentials do not match the one in the database when trying to login, the page should display login error message and only three attempts are permitted before the user is kicked out of the system for 30 minutes

Polly Pipe is a water sports provider and installer based in Braintree, England. They need you to design and implement a database that meets the data requirements. These necessities are defined in this scenario and below are samples of the paper records that the Polly Pipe preserves.

Polly Pipe is focused in placing aquariums at business customers. Customers can request several installations, but each installation is tailor-made for a specific customer. Facilities are classified by type. One or more employees are assigned to each facility. Because these facilities are often very large, they can include carpenters and masons as well as water installers. The facilities use equipment such as aquariums, air pumps and thermostats. There can be multiple computers in a facility.

Below are examples of paper records that Polly Pipe currently maintains.

Create a Entity Relationship Diagram with cardinalities,primary keys,foreign keys,entities and attributes.

Polly Pipe is a water sports provider and installer based in Braintree, England. They need you to design and implement a database that meets the data requirements. These necessities are defined in this scenario and below are samples of the paper records that the Polly Pipe preserves.

Polly Pipe is focused in placing aquariums at business customers. Customers can request several installations, but each installation is tailor-made for a specific customer. Facilities are classified by type. One or more employees are assigned to each facility. Because these facilities are often very large, they can include carpenters and masons as well as water installers. The facilities use equipment such as aquariums, air pumps and thermostats. There can be multiple computers in a facility.

Below are examples of paper records that Polly Pipe currently maintains.

Create an ERD for this.

Exemplify the developer myths with suitable scenario

Get all the potential users. Fetch the user_ids who liked at least 2 videos published by "Disney" channel, and who did not subscribe to the channel (channel_id = 352).

Note:

Consider reaction_type LIKE as liked.

Sort the output in the descending order of no_of_likes, and then in the ascending order of potential_user_id.

Expected Output Format

potential_user_id no_of_likes

table:

View Schema

user_likes

user_id video_id reaction_type reacted_at

video

channel_id

channel

channel_id name owner_id

1) Find the manager who manages most employees but also being managed by someone else .

2) Find the artist name who is the most profitable commercially ? (his/her tracks have been sold the most)

ER-Diagram for this questions

https://i.stack.imgur.com/CX01i.png

Find the name of the German customer(s) who has paid the most in total and is not associated with a company.

Why do we care that the expressions are equivalent? (5) 2.3.3 How can we determine that the expressions are equivalent?