CS403 Midterm Solved Current Paper Fall 2021 by Adil Alvi

Cs 403 midterm solved current paper fall 2021

Q1. Difference between Primary key and alternative key and secondary key 2 points?

A candidate key chosen by the database designer to act as key is the primary key.

Candidate keys which are not chosen as the primary key are known as alternate keys.

Many times we need to access certain instances of an entity type using the value(s) of one or more attributes other than the PK.

2. Standardization ka benifit btana tha future m apny point of view sy

Database Architecture: Standardization of database systems is a very beneficent in terms of future growth, because once a system is defined to follow a specific standard, or is built on a specific standard, it provides us the ease of use in a number of aspects.

3. Cartesian product ka long tha ek

The Cartesian product needs not to be union compatible. It means they can be of different degree. It is denoted by X. suppose there is a relation R with attributes (A1, A2,...An) and S with attributes (B1, B2……Bn). The Cartesian product will be: R X S

4. How data sharing is done in database. Explain. Also give solid example.

The data for different applications or subsystems is placed at the same place. This introduces the major benefit of data sharing. That is, data that is common among different applications need not to be stored repeatedly, as was the case in the file processing environment. For example,systems of an educational institution.

5. Student and Course k attributes given thy mapping krni the Many to Many
6. Two columns thy us mai sy Entity type, Entity instance and Entity set ko separate krna tha

Entity Type

The entity type can be defined as a name/label assigned to items/objects that exist in an environment and that have similar properties. It could be person, place, event or even concept, that is, an entity type can be defined for physical as well as not-physical things.

Entity Instance

A particular object belonging to a particular entity type and how does an item becomes an instance of or belongs to an entity type? By possessing the defining properties associated with an entity type. For example, EMPLOYEE, FURNITURE, ELECTRIC APPLIANCES, OFFICE EQUIPMENT

Entity Set

A group of entity instances of a particular entity type is called an entity set. For example, all employees of an organization form an entity set. Like all students, all courses, all of them form entity set of different entity types

7. Steps of data base

o Database Design o Application Programs o Implementation

8. Is it necessary to normalize relation... Explain

Normalization is a step by step process to make DB design more efficient and accurate. A normalized database helps the DBA to maintain the consistency of the database. However, the normalization process is not a must, rather it is a strongly recommended activity performed after the logical DB design phase

9. 1NF ko 2NF m convert krna th

The process for transforming a 1NF table to 2NF is:

• Identify any determinants other than the composite key, and the columns they determine.
• Create and name a new table for each determinant and the unique columns it determines.
• Move the determined columns from the original table to the new table. The determinate becomes the primary key of the new table.
• Delete the columns you just moved from the original table except for the determinant which will serve as a foreign key.
• The original table may be renamed to maintain semantic meaning.

10. Weak entity explained

In a relational database, a weak entity is an entity that cannot be uniquely identified by its attributes alone; therefore, it must use a foreign key in conjunction with its attributes to create a primary key

11. Three operation of DBMS

In a relational database, three operations are used to develop sets of data: Select: Creates a subset of data of records that meet stated criteria. Join: Combines relational data from different tables. Project: Creates a subset of a table using only specified columns.