Database Interview Questions and Answers
Question - 11 : - What is the main differnce between schema in RDBMS and schemas in DataWarehouse....?
Answer - 11 : - RDBMS Schema
* Used for OLTP systems
* Traditional and old schema
* Normalized
* Difficult to understand and navigate
* Cannot solve extract and complex problems
* Poorly modelled
DWH Schema
* Used for OLAP systems
* New generation schema
* De Normalized
* Easy to understand and navigate
* Extract and complex problems can be easily solved
* Very good model
Question - 12 : - What do you understand by ‘Database’?
Answer - 12 : -
Database is an organized collection of related data where the data is stored and organized to serve some specific purpose.
For Example, A librarian maintain a database of all the information related to the books that are available in the library.
Question - 13 : - Define DBMS.
Answer - 13 : -
DBMS stands for Database Management System. It is a collection of application programs which allow the user to organize, restore and retrieve information about data efficiently and as effectively as possible.
Some of the popular DBMS’s are MySql, Oracle, Sybase, etc.
Question - 14 : - Define RDBMS.
Answer - 14 : - Relational Database Management System(RDBMS) is based on a relational model of data that is stored in databases in separate tables and they are related to the use of a common column. Data can be accessed easily from the relational database using Structured Query Language (SQL).
Question - 15 : - Enlist the advantages of DBMS.
Answer - 15 : -
The advantages of DBMS includes:
- Data is stored in a structured way and hence redundancy is controlled.
- Validates the data entered and provide restrictions on unauthorized access to the database.
- Provides backup and recovery of the data when required.
- It provides multiple user interfaces.
Answer - 16 : - Duplication of data in the database is known as data redundancy. As a result of data redundancy, duplicated data is present at multiple locations, hence it leads to wastage of the storage space and the integrity of the database is destroyed.
Question - 17 : - What are the various types of relationships in Database? Define them.
Answer - 17 : -
There are 3 types of relationships in Database:
- One-to-one: One table has a relationship with another table having the similar kind of column. Each primary key relates to only one or no record in the related table.
- One-to-many: One table has a relationship with another table that has primary and foreign key relations. The primary key table contains only one record that relates to none, one or many records in the related table.
- Many-to-many: Each record in both the tables can relate to many numbers of records in another table.
Answer - 18 : -
Normalization is the process of removing redundant data from the database by splitting the table in a well-defined manner in order to maintain data integrity. This process saves much of the storage space.
Question - 19 : - Explain De-Normalization.
Answer - 19 : -
De-normalization is the process of adding up redundant data on the table in order to speed up the complex queries and thus achieve better performance.
Question - 20 : - What are the different types of Normalization?
Answer - 20 : -
Different types of Normalization are:
- First Normal Form (1NF): A relation is said to be in 1NF only when all the entities of the table contain unique or atomic values.
- Second Normal Form (2NF): A relation is said to be in 2NF only if it is in 1NF and all the non-key attribute of the table is fully dependent on the primary key.
- Third Normal Form (3NF): A relation is said to be in 3NF only if it is in 2NF and every non-key attribute of the table is not transitively dependent on the primary key.