Important Oracle Interview Questions with Answers

Here is a list of 60 interview questions about Oracle Database with their answers. The list contains questions useful for basic, freshers and experienced oracle professionals.Download Complete Oracle Interview Questions PDF. Each question contains their answer also. Its a good practice to go through all of these questions before attending the interview.

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?


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?


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?


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.



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?


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?


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?


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

  1. What is an ALERT?


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?


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?


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

  1. What is hash cluster?


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?


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
  • Question about Clusters
  • Index in database. This is an important section that you should prepare well.
  • What is called as Views in RDBMS. What are the uses
  • Tell about various types of queries that you know
  • Clusterd and non-clusterd index
  • Introduction about Table Space