Oracle PL/SQL Interview Questions and Answers

What is Savepoint?
Savepoint is a point within a particular transaction to which you may rollback without rolling back the entire transaction.
What is difference between a Cursor declared in a procedure and Cursor declared in a package specification ?

A cursor declared in a package specification is global and can be accessed by other procedures or procedures in a package.

A cursor declared in a procedure is local to the procedure that can not be accessed by other procedures.

What are the various types of Exceptions ?

User defined and Predefined/System defined Exceptions.

What are the various types of database triggers ?
There are 12 types of triggers, they are combination of : Insert, Delete and Update Triggers. Before and After Triggers. Row and Statement Triggers.
What are the advantages/disadvantages of clusters ?
advantages : Access time reduced for joins. disadvantages : The time for Insert increases.
What is a forward declaration ? What is its use ?
PL/SQL requires that you declare an identifier before using it.Therefore, you must declare a subprogram before calling it.This declaration at the start of a subprogram is called forward declaration.A forward declaration consists of a subprogram specification terminated by a semicolon.
What are the types of Notation ?
Position, Named, Mixed and Restrictions.
If I have an execute privilege on a procedure in another users schema, can I execute his procedure even though I do not have privileges on the tables within the procedure ?
Yes

What is the advantage of using packages for storing PL/SQL objects?

Packages offer several advantages when you call a packaged subprogram for the first time, the whole package is loaded into memory. So, later calls to related subprograms in the package require no disk I/O.
Packaged public variables and cursors persist for the duration of a session. So, they can be shared by all subprograms that execute in the environment.
You can specify public (visible and accessible) or private (hidden and inaccessible) in Package.

Define exception and How will you raise an exception in PL/SQL procedure?

In PL/SQL, a error condition is called an exception. Exceptions can be system defined or user defined.

Examples of system defined exceptions include division by zero and out of memory. Some common system exceptions have predefined names, such as ZERO_DIVIDE and STORAGE_ERROR.
You can define exceptions of your own in the declarative part of any PL/SQL block, subprogram, or package. Unlike system defined exceptions, user-defined exceptions must be declared and must be raised explicitly by RAISE statements.

The following example illustrates the scope rules:

DECLARE
due EXCEPTION; 
BEGIN
RAISE due; 
EXCEPTION
WHEN due THEN 
Null;
END; 

What is the difference between Procedure and Function?

Differences between Functions and Procedures

-Functions are normally used for computations where as procedures are normally used for executing business logic.

-Functions must return a value (using the RETURN keyword), but for stored procedures this is not compulsory. Procedures can use RETURN keyword but without any value being passed.

-Functions could be used in SELECT statements, but they should don't do any data manipulation. However, procedures cannot be included in SELECT statements.

-Functions could be used in creating "Function Based Indexes" to improve the performance ,but procedure not.

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Pipes and Cistern

Two pipes A and B can fill a tank in 6 hours and 4 hours respectively. If they are opened on alternate hours and if pipe A s opened first, in how many hours, the tank shall be full?

A large tanker can be filled by two pipes A and B in 60 min and 40 min respectively. How many minutes will it take to fill the tanker from empty state if B is used for first half of the time, and A and B fill it together for the other half?

A tank is filled by 3 pipes with uniform flow. The first two pipes operating simultaneously fill the tank in the same time during which the tank is filled by the third pipe alone. The 2nd pipe fills the tank 5 hours faster than first pipe and 4 hours slower than third pipe. The time required by first pipe is?

Two pipes A and B together can fill a cistern in 4 hours. Had they been opened separately, then B would have taken 6 hours more than A to fill the cistern. How much time will be taken by A to fill the cistern separately?

Two pipes A and B can fill a tank in 24 min and 32 min respectively. If both the pipes are opened simultaneously, after how much time B should be closed so that the tank is full in 18 min?

Two pipes A and B can fill a tank in 36 min and 45 min respectively. A water pipe C can empty the tank in 30 min. First A and B are opened. after 7 min, C is also opened. In how much time, the tank is full?

Two pipes can fill a cistern in 14 hours and 16 hours respectively. The pipes are opened simultaneously and it is found that due to leakage in the bottom it took 32 min more to fill the cistern. When the cistern is full, in what time will the leak empty it?

Bucket P has thrice the capacity as Bucket Q. It takes 60 turns for Bucket P to fill the empty drum. How many turns it will take for both the buckets P and Q, having each turn together to fill the empty drum?

Probability

In a class , 30 % of the students offered English, 20 % offered Hindi and 10 % offered Both.If a student is offered at random, what is the probability that he has offered English or Hindi?

In a lottery ,there are 10 prizes and 25 blanks.A lottery is drawn at random. what is the probability of getting a prize ?

Two dice are thrown simultaneously .what is the probability of getting two numbers whose product is even?

Two diced are tossed the probability that the total score is a prime number?

Two cards are drawn at random from a pack of 52 cards What is the probability that either both are black or both are queens?

Two dice are thrown together .What is the probability that the sum of the number on the two faces is divisible by 4 or 6?

A bag contains 6 white and 4 black balls .Two balls are drawn at random .Find the probability that they are of the same colour?

In a simultaneous throw of a pair of dice,find the probability of getting a total more than 7?

An unbiased die is tossed.Find the probability of getting a multiple of 3?

Problems on Ages

My brother is 3 years elder to me. My father was 28 years of age when my sister was born while my mother was 26 years of age when i was born. If my sister was 4 years of age when my brother was born,then what was the age my father and mother respectively when my brother was born?

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