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Oracle Corporation is a multinational computer technology corporation based in Redwood Shores, California in USA. Its main areas of specialization include developing and marketing database software and technology, enterprise software products and cloud engineered systems. Oracle was second to Microsoft in terms of the highest revenue generation by a software making company in 2015.

The company equally designs and develops tools used in database development and middle-tier software systems, enterprise resource planning (ERP) software, software for supply chain Management(SCM), and software for customer relationship management (CRM)

Oracle Interview Questions and Answers

Are you preparing to attend an Oracle interview soon? Here are a few questions and answers you may find interesting.

  1. What is RAW datatype?

Ans. RAW data type is used in storing values in binary data format. The maximum size of a RAW in a table is 32767 bytes.

  1. What is BLOB datatype?

Ans. A BLOB data type is a binary string with a varying length which is used in storing two gigabytes memory. Length should be stated in Bytes for BLOB

  1. What is NULL value in Oracle?

Ans. NULL value represents unknown or missing data. It is used as a place holder or represented as a default entry indicating that no actual data is present.


Ans. The WITH CHECK option clause specifies the level of check to be done in DML statements. It aids in preventing changes to a view that would produce results not contained in the sub query.

  1. What is the difference between varchar and varchar2 data types?

Ans. Varchar can store up to 2000 bytes and varchar2 can store up to 4000 bytes. While Varchar will occupy space for NULL value, Varchar2 will not occupy any space. They are differentiated by space.

  1. What is the use of NVL function?

Ans. The NVL function is used for replacing NULL values with given or another value. E.g.  NVL(Value, replace value)

  1. How do we get field detail of a table?

Ans. To get the field of a specified table use, Describe <Table_Name>

  1. What is an ALERT?

Ans. An alert is a window which appears in the center of the screen and overlays a portion of the current play.

  1. What is the fastest query method to fetch data from the table?

Ans. You can use ROWID to fetch Row from the table. The use of ROW ID is the fastest query method for fetching data from the table.

  1. What is the parameter mode that can be passed to a procedure?

Ans. The parameter modes that can be passed to a procedure are IN, OUT and INOUT

  1. What is hash cluster?

Ans. Hash Cluster is a technique used for storing the table to make it faster to retrieve. It order to retrieve the rows from the table, apply the hash value on the table.

  1. What are SET operators?

Ans. SET operators are used with two or more queries. The operators are Union, Union All, intersect and Minus.

What is a view? View is a logical table that is based on one or more tables and views. The tables which the view is based upon are called Base Tables and it contains no data.

  • Expect this as the first questions, if you are a fresher. Prepare answer for an introduction about Oracle
    2_What is Oracle table
  • Question about Clusters
    3_What are Clusters
  • Index in database. This is an important section that you should prepare well.
    4_What is an Index
  • What is called as Views in RDBMS. What are the uses
    5_What are the advantages of views
  • Tell about various types of queries that you know
    6_What are the various types of queries
  • Clusterd and non-clusterd index
    7_What is the difference between clustered and a non-clustered index
  • Introduction about Table Space
    8_What is a Tablespace
  • 9_Why use materialized view instead of a table
  • 10_What does ROLLBACK do
  • 11_Compare and contrast TRUNCATE and DELETE for a table
  • 12_what is null value
  • 13_Define transaction
  • 14_what is the difference between sql&oracle
  • 15_What are different Oracle database objects
  • 16_What is hash cluster
  • 17_What is a User_exit
  • 18_What is schema
  • 19_What are Roles
  • 20_What are the dictionary tables used to monitor a database spaces
  • 21_What is a SNAPSHOT
  • 22_What is a database instance
  • 23_What are parameters
  • 24_What are the different file extensions that are created by oracle reports
  • 25_What are clusters
  • 26_What is difference between SUBSTR and INSTR
  • 27_Define a view
  • 28_What is the difference between a view and a synonym
  • 29_What is the usage of SAVEPOINTS
  • 31_When do you use WHERE clause and when do you use HAVING clause
  • 32_What are the differences between stored procedures and triggers
  • 33_What must be installed with ODBC on the client in order for it to work with Oracle
  • 34_What are the different file extensions that are created by oracle reports
  • 35_what is trigger
  • 36_Explain the difference between a data block an extent and a segment
  • 37_What is bind reference and how can it be created
  • 38_How many LONG columns are allowed in a table Is it possible to use LONG columns in WHERE clause or ORDER BY
  • 39_What are various types of joins
  • 40_What is the maximum number of triggers can apply to a single table
  • 41_What command would you use to create a backup control file
  • 42_What is an Oracle index
  • 43_What are the different index configurations a table can have
  • 44_What is difference between UNIQUE constraint and PRIMARY KEY constraint
  • 45_What is BCP When does it used
  • 46_How to know which index a table is using
  • 47_What is SYSTEM tablespace and when is it created
  • 48_Which date function returns number value Which date function returns number value
  • 49_what is integrity constrains
  • 50_What is the difference between Explicit and Implicit Cursors
  • 51_what are primary keys
  • 52_What are the components of physical database structure of Oracle database
  • 53_What is DECODE function used for
  • 54_What is the default return value of a function
  • 55_What is the difference between oraclesql and sql server
  • 56_How you will avoid your query from using indexes
  • 57_What is a cluster key
  • 58_What is SGA
  • 59_What is a data segment
  • 60_What is ROWID
  • 61_What is the usage of SAVEPOINTS
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