Give an example of a data constraint and an example of a business rule. Be sure

Question

Give an example of a data constraint and an example of a business rule. Be sure to label which is which so I can tell you know the difference.

Explain the difference between an entity class and an entity instance, and give an example other than those used in the text or the lectures.

Define the term “weak entity” and give an example other than those used in the text.

Define supertype, subtype and discriminator.

Explain the difference between and inclusive subtype relationship and an exclusive subtype relationship.

Using Microsoft Visio 2013 (available through Microsoft Imagine) draw an IE Crow’s Foot E-R diagram for the entities DEPARTMENT and EMPLOYEE. A DEPARTMENT may have more than one EMPLOYEE, but an EMPLOYEE is only assigned to one DEPARTMENT. Assume that a DEPARTMENT does not need to have an EMPLOYEE, but that every EMPLOYEE is assigned to a DEPARTMENT. Include at least three appropriate identifiers and attributes for each entity.

Explain the following crow’s foot E-R diagram. Be sure to include entities, keys, attributes, cardinality. What is the special type of entity represented by COMMISSION_RATE?

Explanation / Answer

Business Rules

Basically Business rules are obtained from the end users when we want to collect requirements of users These rules are verified by the user before we design the database . If the business rules are incorrect it adversely affect the design and ultimately the application built will not function as expected/required by the users.

Some examples of business rules are:

Where as ,

Data Constraints are some guided rules basically used to limit the type of data that can br come under a defined table, to maintain the nn-redundency and integrity of the data inside that table.

Let us assume there is a table with more than one column ,in which one column is for mobile number and if you want to allow only distinct contact numbers of the user you can use Unique key constraint.

For other questions to be answered please provide as seprate questions

Thankyou

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