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Oracle Interview Questions

Oracle Interview Questions: After a skill-based Oracle training, aspirants now have to materialize for job interviews. Contributing relevant answers to Oracle interview question can lend a hand in deciding the prospect of the applicants. Thus, it is highly significant to answer successfully during the interview sessions so that contributors can come across a way to attain their career goals. This is an article containing Oracle interview questionnaire. The piece of writing has been arranged by Oracle specialists, Oracle experts, and Oracle trainers who have used their best of their knowledge while developing the Oracle interview questions and answers for freshers, and experience aspirants. The questionnaire contains detailed answers covering basic and advanced Oracle interview questions. Understanding of each question and answer provided in the article would assists job aspirants to crack interviews and discover relevant answers to their doubts or puzzlements. The Oracle Interview Questions is a summarization of verticals available in the Oracle technology.

oracle interview questions

About Oracle

Oracle database (Oracle DB) is a relational database management system (RDBMS). Oracle DB is the most believed and widely used database engines. The database is built in the order of a relational database framework, which comprehend the data objects directly. Users can access the database through structured query language (SQL). Oracle is fully scalable relational database architecture. The database is used mostly by the enterprises that have their businesses or offices located across the different continents. Oracle helps in managing and processing data across wide and local area networks. Oracle is all about data performance, data availability, security, compliance, administrating Oracle Database products, etc. Students need to manage and configure data, data centers, hybrid or pure cloud configuration, or even run a large data management cloud service, and so on.

Oracle Interview Questions And Answers

1. What is Oracle?

Oracle is a company. Oracle is also a database server, which manages data in a very structured way. It allows users to store and retrieve related data in a multi-user environment so that the users can concurrently access the same data. All this is accomplished while delivering high performance. A database server also prevents unauthorized access and provides efficient solutions for failure recovery. A standby database is a database replica created by taking a backup of a primary database.

2. What is an Oracle Database?

Oracle provides software to create and manage the Oracle Database. The database consists of physical and logical structures in which system, user, and control information are stored. The software that manages the database is called the Oracle Database server. Collectively, the software that runs Oracle and the physical database is called the Oracle Database system.

A database buffer cache stores the data in memory for quicker access. The redo logs track and store all the changes made to the database. A Data Guard ensures data protection and high availability of data, and a control file records the physical structure of the database.

3. What are the roles of DBA?

A DBA has the authority to create new users, remove the existing users, or modify any of the environment variables or privileges assigned to other users.

  • Manage database storage
  • Administer users and security
  • Manage schema objects
  • Monitor and manage database performance
  • Perform backup and recovery
  • Schedule and automate jobs

4. What are the different Oracle Database objects?

  • Tables
  • Views
  • Indexes
  • Synonyms
  • Sequences
  • Tablespaces

5. What are the benefits of ORDBMS?

In ORDBMS, the objects can be stored as they are. The language of the DBMS can be integrated with an object-oriented programming language. The language may even be exactly the same as that used in the application, which does not force the programmer to have two representations of his objects.

6. What are the components of physical database structure of Oracle database?

Components of physical database structure are given below.

  • One or more data files.
  • Two or more redo log files.
  • One or more control files.

7. What are the components of logical database structure in Oracle database?

Components of logical database structure.

8. What is a tablespace?

A database contains Logical Storage Unit called tablespaces. A tablespace is a set of related logical structures. Actually a tablespace groups related logical structures together.

9. What is a SYSTEM tablespace and when it is created?

When the database is created in Oracle database system, it automatically generate a SYSTEM named SYSTEM tablespace. The SYSTEM tablespace contains data dictionary tables for the entire database.

10. What is an Oracle table?

A table is basic unit of data storage in Oracle database. A table contains all the accessible information of a user in rows and columns.

11. In the Oracle version, what does each number shows?

Oracle version number refers:

  • 9 - Major database release number
  • 3 - Database maintenance release number
  • 0 - Application server release number
  • 5 - Component Specific release number
  • 0 - Platform Specific release number

12. Difference between varchar and varchar2 data types?

Varchar can store upto 2000 bytes and varchar2 can store upto 4000 bytes. Varchar will occupy space for NULL values and Varchar2 will not occupy any space. Both are differed with respect to space.

13. In which language Oracle has been developed?

Oracle has been developed using C Language.

14. What is RAW datatype?

RAW datatype is used to store values in binary data format. The maximum size for a raw in a table in 32767 bytes.

15. What is the use of NVL function?

The NVL function is used to replace NULL values with another or given value. Example is –

NVL(Value, replace value)

16. Whether any commands are used for Months calculation? If so, What are they?

In Oracle, months_between function is used to find number of months between the given dates. Example is –

Months_between(Date 1, Date 2)

17. What are nested tables?

Nested table is a data type in Oracle which is used to support columns containing multi valued attributes. It also hold entire sub table.

18. What is COALESCE function?

COALESCE function is used to return the value which is set to be not null in the list. If all values in the list are null, then the coalesce function will return NULL.

Coalesce(value1, value2,value3,…)

19. What is BLOB datatype?

A BLOB data type is a varying length binary string which is used to store two gigabytes memory. Length should be specified in Bytes for BLOB.

20. How do we represent comments in Oracle?

Comments in Oracle can be represented in two ways –

  1. Two dashes(–) before beginning of the line – Single statement
  2. /*—— */ is used to represent it as comments for block of statement

21. What is DML?

Data Manipulation Language (DML) is used to access and manipulate data in the existing objects. DML statements are insert, select, update and delete and it won’t implicitly commit the current transaction.

22. What is the difference between TRANSLATE and REPLACE?

Translate is used for character by character substitution and Replace is used substitute a single character with a word.

23. How do we display rows from the table without duplicates?

Duplicate rows can be removed by using the keyword DISTINCT in the select statement.

24. What is a NVL function? How can it be used?

NVL is a function, which helps the user to substitute a value if null is encountered for an expression.

It can be used as the below syntax.

[NVL (Value_In, Replace_With)]

25. What is the difference between a Primary Key & a Unique Key?

Primary key is used to identify each table row uniquely, while a Unique Key prevents duplicate values in a table column. Given below are few differences:

  • The primary key can be only one on the table while unique keys can be multiple.
  • The primary key cannot hold null value at all while Unique key allows multiple null values.
  • The primary key is a clustered index while a unique key is a non-clustered index.

26. What is the use of Aggregate functions in Oracle?

Aggregate functions perform summary operations on a set of values to provide a single value. There are several aggregate functions that we use in our code to perform calculations.

Few of them are listed below:

  • AVG
  • MIN
  • MAX
  • SUM

27. What are the set operators UNION, UNION ALL, MINUS & INTERSECT meant to do?

Set operator facilitates the user to fetch the data from two or more than two tables at once if the columns and relative data types are same in the source tables.

  • UNION operator returns all the rows from both the tables except the duplicate rows.
  • UNION ALL returns all the rows from both the tables along with the duplicate rows.
  • MINUS returns rows from the first table, which does not exist in the second table.
  • INTERSECT returns only the common rows in both the tables.

28. What is meant by a deadlock situation?

Deadlock is a situation when two or more users are simultaneously waiting for the data, which is locked by each other and hence, results in all blocked user sessions.

29. What is meant by an index?

An index is a schema object, which is created to search the data efficiently within the table. Indexes are usually created on certain columns of the table, which are accessed the most.

Indexes can be clustered or non-clustered.

30. What are the parameters that we can pass through a stored procedure?

We can pass IN, OUT & INOUT parameters through a stored procedure and they should be defined while declaring the procedure itself.

Career scopes and salary scale

Every sector in the industry is watching a job crunch. However, when it is about Artificial Intelligence and Oracle, the need for skilled professionals of Oracle are at higher side. Oracle participants having in-depth knowledge and obtained skill-based training are able to discover better career opportunities in the worldwide job marketplaces. Besides, Oracle has occupied the topmost place in the arena of Artificial Intelligence. A Oracle participants is expected a minimum salary of 42, 000 dollars per annum. However, the salary of an experienced Oracle expert can reach to its double. The salaries are very reliant upon the location, business, and the company’s requirements.


The article ‘Oracle interview questions’ has been prolifically answered every advanced Oracle interview questions. As well, the understanding approach in the Oracle interview questions for experienced is being intended by our trainers and team of experts. They have tried their top of the familiarity to help professionals in getting answers to all doubts and not clear concepts. Even then, if learners still require more detailing about Oracle, they may drop in a message to our experts concerning to Oracle interview questions for experienced professionals. Our trainers would be happy to assist and resolve all your Oracle-programming issues of the students. Join Oracle Training in Noida, Oracle Training in Delhi, Oracle Training in Gurgaon

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