Oracle SQL Interview Questions and Answers

What is Correlated Subquery?
Correlated Subquery is a subquery that is evaluated once for each row processed by the parent statement. Parent statement can be Select, Update or Delete.
What is Sequence?
Sequences are used for generating sequence numbers without any overhead of locking. Drawback is that after generating a sequence number if the transaction is rolled back, then that sequence number is lost.
What is the Purpose of HAVING Clause?
The HAVING clause is used in combination with the GROUP BY clause. It can be used in a SELECT statement to filter the records that a GROUP BY returns.
What is INLINE View in SQL?
The inline view is a construct in Oracle SQL where you can place a query in the SQL FROM, clause, just as if the query was a table name.
Does the view exist if the table is dropped from the database?
Yes, in Oracle, the view continues to exist even after one of the tables (that the view is based on) is dropped from the database. However, if you try to query the view after the table has been dropped, you will receive a message indicating that the view has errors.
What is the difference between a “where” clause and a “having” clause?

“Where” is a kind of restriction statement. You use where clause to restrict all the data from DB. Where clause is used before result retrieving. 

Having clause is using after retrieving the data. Having clause is a kind of filtering command.

What is the difference between the snapshot and synonym?
A snapshot refers to read-only copies of a master table or tables located on a remote node. A snapshot can be queried, but not updated; only the master table can be updated. A snapshot is periodically refreshed to reflect changes made to the master table. In this sense, a snapshot is really a view with periodicity. A synonym is an alias for table, view, sequence or program unit. They are of two types private and public.
What is the difference between data types char and varchar?
Char reserves the number of memory locations mentioned in the variable declarations, even though not used. Where as Varchar does not reserve any memory locations when the variable is declared, it stores the values only after they are assigned.
What is Rowid?
It is a Hexadecimal Representation of a Row in a Table. Rowid can only be Changed if we ‘Enable Row Movement’ on a Partitioned Table. Rowid’s of Deleted Rows can be Reused if Transaction is Committed.
What is the Difference between Translate & Replace?
Translate function converts each character in String with specified one whereas Replace function replaces part of the string in continuity by another sub-string.
What is NVL?
NVL: Null value function converts a null value to a non-null value for the purpose of evaluating an expression.
Operators used in SELECT statements are?
= Equal <> or != Not equal > Greater than < Less than >= Greater than or equal <= Less than or equal BETWEEN Between an inclusive range LIKE Search for a pattern

Latest Updates


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Time and Distance

A thief is spotted by a policeman from a distacne of 100 m. When the policeman starts the chase, the thief also starts running. If the speed of the theif is 8 km / hour and that of the policeman is 10 km/hour, then how far will the theif have to run before he is overtaken?


Aman and Alok attempted to solve a quadratic equation. Aman made a mistake in writing down the constant term and ended up in roots (4, 3). Alok made a mistake in writing down the coefficient of x to get roots (3, 2). The correct roots of the equation are?

Compound Interest

The effective annual rate of interest corresponding to a nominal rate of 22% per annum payable half-yearly is?

Volume and Surface Area

If the volume of a cylinder is 2156 cubic cm and height is 14 cm, find its radius?


What is the equation of the line which passes through the points (2, 3) and (- 4, 1)?


In △ABC, the angle bisector of ∠A cuts BC at E. Find length of AC, if lengths of AB, BE and EC are 9 cm, 3.6 cm and 2.4 cm?

In a triangle, the length of the opposite side of the angle which measures 45° is 8√2 cm, what is the length of the side opposite to the angle which measures 90°?

General Knowledge of India

The boundary line between India and Pakistan is called?

Which city is located on the banks of the river Mahanadi?

Indian History

When was the battle of Haldighati fought?

In 1498, which Portuguese explorer discovered a new sea route from Europe to India?

General Knowledge of India

Chapchar Kut is a festival of which State?


In chemistry, soap is a salt of a ?

Indian Economy

Which of the following is a Direct tax?


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A factory buys 8 machines.3 Machine A, 2 Machine B and rest Machine C. Prices of the machines are 100000, 80000 and 45000 respectively.Calculate the average cost of these machines?


Ticket for an adult is 500 and a child is 200. 1 child goes free with two adults. If a group has 20 adults and 8 children what will be the discount the group get?