Database Interview Questions and Answers
Question - 31 : - When is functional dependency said to be the fully functional dependent?
Answer - 31 : -
To fulfill the criteria of fully functional dependency, the relation must meet the requirement of functional dependency.
A functional dependency ‘A’ and ‘B’ are said to be fully functional dependent when removal of any attribute say ‘X’ from ‘A’ means the dependency does not hold anymore.
Question - 32 : - What do you understand by the E-R model?
Answer - 32 : -
E-R model is an Entity-Relationship model which defines the conceptual view of the database.
The E-R model basically shows the real-world entities and their association/relations. Entities here represent the set of attributes in the database.
Question - 33 : - Define Entity, Entity type, and Entity set.
Answer - 33 : -
Entity can be anything, be it a place, class or object which has an independent existence in the real world.
Entity Type represents a set of entities that have similar attributes.
Entity Set in the database represents a collection of entities having a particular entity type.
Question - 34 : - Define a Weak Entity set.
Answer - 34 : - Weak Entity set is the one whose primary key comprises its partial key as well as the primary key of its parent entity. This is the case because the entity set may not have sufficient attributes to form a primary key.
Question - 35 : - Explain the terms ‘Attribute’ and ‘Relations’
Answer - 35 : -
Attribute is described as the properties or characteristics of an entity. For Example, Employee ID, Employee Name, Age, etc., can be attributes of the entity Employee.
Relation is a two-dimensional table containing a number of rows and columns where every row represents a record of the relation. Here, rows are also known as ‘Tuples’ and columns are known as ‘Attributes’.
Question - 36 : - What are VDL and SDL?
Answer - 36 : -
VDL is View Definition Language which represents user views and their mapping to the conceptual schema.
SDL is Storage Definition Language which specifies the mapping between two schemas.
Question - 37 : - Define Cursor and its types.
Answer - 37 : -
Cursor is a temporary work area that stores the data, as well as the result set, occurred after manipulation of data retrieved. A cursor can hold only one row at a time.
The 2 types of Cursor are:
- Implicit cursors are declared automatically when DML statements like INSERT, UPDATE, DELETE is executed.
- Explicit cursors have to be declared when SELECT statements that are returning more than one row are executed.
Answer - 38 : - Sequence of operation performed which changes the consistent state of the database to another is known as the database transaction. After the completion of the transaction, either the successful completion is reflected in the system or the transaction fails and no change is reflected.
Question - 39 : - Define Database Lock and its types.
Answer - 39 : -
Database lock basically signifies the transaction about the current status of the data item i.e. whether that data is being used by other transactions or not at the present point of time.
There are two types of Database lock: Shared Lock and Exclusive Lock.
Question - 40 : - What is Data Warehousing?
Answer - 40 : - The storage as well as access to data, that is being derived from the transactions and other sources, from a central location in order to perform the analysis is called Data Warehousing.