All The Useful RDBMS Interview Questions & Answers

Relational database management system (RDBMS) is a subset of DBMS. In RDBMS, the relational database indicates that the data is stored in the structure format using the rows and the columns, i.e., tables and the values in each table are related to each other. 

RDBMS software executes the queries on the data like adding and updating the data. 

Some of the most popular RDBMS software are SQL Server, Oracle, PostgreSQL, SQLite, ThinkSQL, Cubrid.

Advantages of RDBMS:
RDBMS is in tabular form which is easy to understand
Provide Security
Easy to maintain, repair and test
Multiuser access to the database in real time
Easy to learn and implement.

Q 1. How is RDBMS different from DBMS?

DBMS    Vs    RDBMS

1.    DBMS store data as a file    - RDBMS store data in tabular form.
2.    DBMS handle a small amount of data    - RDBMS handle a large amount of data
3.    Normalization is absent in DBMS    - Normalization is present in RDBMS

Q 2. What is RDBMS and also explain its components?
RDBMS stands for the Relational Database Management System.RDBMS is the DBMS in which the data is stored in the tables, i.e., the values are stored in the rows and columns.

The components of RDBMS are: 
Tables: Table holds the records for one entity whose information has to be saved. Here every row contains a record, and every column represents an attribute.
Forms: Forms are used to enter the new record into the database.

Queries: Queries are used to search the data across the tables to executes the queries.
Reports: Reports are used to organize the query results in a proper way.
Macros: provides the more features and the extra functionality to the database.
Modules: Programmers can write the modules in their respective programming language and then run the blades when they are required from the database.

Q 3. What is the difference between primary and foreign key?

Primary Key Vs Foreign Key

1.    Value cannot be NULL -    Value can be NULL
2.    Duplicate values not allowed - Duplicate values are allowed
3.    The primary key can only be one     - There can be multiple foreign key

Q 4. Explain the advantages of RDBMS.

It can be used by more than one users at the same time
Reduces the data redundancy and data duplication
RDBMS provided multiple interfaces
RDBMS is secure

Q 5. Explain, why RDBMS is better than DBMS.

RDBMS handles a large quantity of Data.
RDBMS has very high-end security
RDBMS supports client-server architecture
RDBMS supports multiple users
RDBMS has minimum data redundancy

Q 6. What do you mean by E-R Model & Object-oriented Model?
An Entity-Relationship model is primarily used to represent the real scenarios as entities. E-R model clearly defines the objects and the relations between the entities

An Object-oriented Model is mainly used to represent the real scenarios as objects. The objects with similar functions are grouped and linked to the other different purposes.in this model, the data can be reused in various missions.

Q 7. Explain all Codd's rules for relational database system.
Codd's rules or Codd's law are the set of 12 states which was developed by E.F. Codd in the year 1969-1970. Codd's law tells what is required from the database management system so that it can be considered relational.in other words, Codd's rules are rules for designing the RDBMS.

Rule 1: Information rule: All the information has to be represented in only one way in the table
Rule 2:Guaranteed Access: Every value in the table has to be accessible by the Table Name + Primary Key(Row) + Attribute(column).
Rule 3: Systematic treatment of NULL: NULL values should be treated systematically
Rule 4: Active Online Catalog: The catalog must be stored online
Rule 5: Powerful and Well-Structured Language: -A structured language should provide all access to the data which is stored in the database.
Rule 6: View Updation Rule: All the view has to be updatable by the database system
Rule 7: Relational Level Operation: There has to be the Insert, Delete, Update operations at every level of the relations
Rule 8: Physical Data Independence: The changes in the Physical storage of the data should not affect the database system.
Rule 9: Logical Data Independence: The changes in the logical structure of the database should not change the user view of the data.
Rule 10: Integrity Independence: The Key and the Check constraints, the trigger, etc., should be stored in the Data Dictionary.
Rule 11: Distribution Independence: -A database should work correctly even if it is distributed across the network
Rule 12:Nonsubversion Rule: If the low-level access has been allowed to a system; then it should not be able to subvert the integrity rules to alter the data.

Q 8. What do you mean by super key, primary key, foreign key and candidate key?

Super Key: This key recognizes the row in the table.
Primary Key: This key is a column in the table which recognizes each row in the same table uniquely
Candidate Key: This key does not have any repeated attribute
Foreign Key: This key a column in the table to create a relationship with another table.
 

Q 9. Explain the difference between physical and logical data independence.
In Logical Data Independence the logical schema is modified without rewriting the application programs whereas in Physical Data Independence the physical schema is changed without rewriting the application programs.

Q 10. What do you mean by cardinality and its types?
In the context of data models, cardinality means the relationship between two tables.

The connection can be of 4 types:

One to One: One row of the first table partners with one row of the second table
One to Many: One row of the first table partners with more than one rows of the second table
Many to One: More than one rows of the first table partners with one row of the second table
Many to Many: More than one rows of the first table partners with more than one rows of the second table
In the context of Query Optimization, Cardinality refers to the uniqueness of the column in the table. A column having unique value will have high cardinality and vice-versa.

Q 11. What do you mean by buffer manager?
The subsystem responsible for the allocation of buffer space is called the buffer manager. The buffer manager handles all requests for blocks of the database. If the block is already in main memory, the address in main memory is given to the requester.