Oracle PL/SQL Interview Questions and Answers

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?

A function is a subprogram written to perform certain computations ,
Functions must return a value (using the RETURN keyword), but for stored procedures this is not compulsory. Stored procedures can use RETURN keyword but without any value being passed. 
Functions could be used in SELECT statements, provided they don't do any data manipulation. However, procedures cannot be included in SELECT statements. 

What is PL/SQL ?
SQL is a declarative language that allows database programmers to write a SQL declaration and hand it to the database for execution. As such, SQL cannot be used to execute procedural code with conditional, iterative and sequential statements. To overcome this limitation, PL/SQL was created. PL/SQL is Oracle's Procedural Language extension to SQL.using plsql we perform Conditional Control ,Iterative Sequential Control Statements.it is commonly used to write data-centric programs to manipulate data in an Oracle database.
What is the difference between SQL and PL/SQL?
Both SQL and PL/SQL are languages used to access data within Oracle databases. SQL is a limited language that allows you to directly interact with the database. You can write queries (SELECT), manipulate objects (DDL) and data (DML) with SQL. PL/SQL is a programming language that includes all the features of most other programming languages. its easily integrate with SQL. SQL is executed one statement at a time. PL/SQL is executed as a block of code. SQL tells the database what to do (declarative), not how to do it. In contrast, PL/SQL tell the database how to do things (procedural).
What is the Difference between PL/SQL Table & Nested Table?
PL/SQL Table: Index by Tables are not Stored in Database. Nested Table: Nested Tables are Stored in Database as Database Columns.

What is the Sequence of Firing Database Triggers?

a) Before Statement Level Trigger
b) Before Row Level Trigger
c) After Row Level Trigger
d) After Statement Level Trigger

What is Instead Of Trigger?
This trigger is used to perform DML operation directly on the underlying tables, because a view cannot be modified by normal DML Statements if it contains joins or Group Functions. These triggers are Only Row Level Triggers. The CHECK option for views is not enforced when DML to the view are performed by Instead of Trigger.
Give some important Oracle supplied packages?

DBMS_SQL: It is used to write Procedures & Anonymous blocks that use Dynamic SQL.

DBMS_JOB: Using it, we can submit PL/SQL programs for execution, execute PL/SQL programs on a schedule, identify when programs should run, remove programs from the schedule & suspend programs from running.

DBMS_OUTPUT: This package outputs values & messages from any PL/SQL block.

UTL_FILE: With this package, you can read from & write to Operating system files

UTL_HTTP: This package allows to make HTTP Requests directly from the database.

Give some most often used system defined exceptions?

a) NO_DATA_FOUND (Select Statement returns no rows)
b) TOO_MANY_ROWS (Single row Select statement returns more than 1 row)
c) INVALID_CURSOR (Illegal cursor operations occurred)
d) CURSOR_ALREADY_OPEN (If cursor is opened & we are trying to reopen it)
e) INVALID_NUMBER (Conversion of Character to number fails) f) ZERO_DIVIDE
g) DUP_VAL_ON_INDEX (Attempted to insert a duplicate value)

What is a mutating and constraining table?

“Mutating” means “changing”. A mutating table is a table that is currently being modified by an update, delete, or insert statement. When a trigger tries to reference a table that is in state of being changed, it is considered “mutating” and raises an error since Oracle should not return data that has not yet reached its final state. Another way this error can occur is if the trigger has statements to change the primary, foreign or unique key columns of the table off which it fires.

Can one call DDL statements from PL/SQL?
One can call DDL statements like CREATE, DROP, TRUNCATE, etc. from PL/SQL by using the “EXECUTE IMMEDATE” statement.
What is Commit, Rollback and Save point?

Commit – Makes changes to the current transaction permanent. It erases the savepoints and releases the transaction locks.

Savepoint –Savepoints allow to arbitrarily hold work at any point of time with option of later committing. They are used to divide transactions into smaller portions.

Rollback – This statement is used to undo work.

How do you make a Function and Procedure as a Private?
Functions and Procedures can be made private to a package by not mentioning their declaration in the package specification and by just mentioning them in the package body.
What is the difference between Package, Procedure and Functions?

A package is a database objects that logically groups related PL/SQL types, objects, and Subprograms.

Procedure is a sub program written to perform a set of actions and can return multiple values.

Function is a subprogram written to perform certain computations and always return a value.

What are the modes for passing parameters to Oracle?

There are three modes for passing parameters to subprograms
IN – An In-parameter lets you pass values to the subprogram being called. In the subprogram it acts like a constant and cannot be assigned a value.
OUT – An out-parameter lets you return values to the caller of the subprogram. It acts like an initialized variable its value cannot be assigned to another variable or to itself.
INOUT – An in-out parameter lets you pass initial values to the subprogram being called and returns updated values to the caller.

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General Knowledge of India

Which of the following dance forms was introduced by the great Vaishnava saint and reformer Mahapurusha Sankaradeva ?

Which of the following is the only classical dance of india having links with Muslim culture and represents a unique synthesis of Hindu and Muslim genius in art ?

Time and Distance

Starting from the same point at the same time, Ruhan and Yuvan had to reach the same destination. While Ruhan drove at 45 km/hr, Yuvan was slower by 5 km/hr. If Yuvan arrived at the destination an hour after Ruhan did, the distance covered by each, in Kilometres, was ?

Simple Interest

A sum of money was invested at a certain rate of simple interest for 4 years. Had the sum been invested at a rate 3% higher than the actual rate, the interest earned would have been 720 Rs more. Find the sum initially invested?

Ratio and Proportion

A bag contains red, blue and black balls. The ratio of red to blue balls is 3 : 5. The ratio of black to red balls is 3 : 4. What is the ratio of blue to black balls?

Profit and Loss

Selling a pack of incense sticks for 136 Rs resulted in a loss of 15%. To make a profit of 10%, the selling price should be ?

Percentage

23% of a bucket full of diluted milk was water. If the quantity of pure milk in the bucket was 15.4 liter, then the capacity of the bucket was ?

Average

The average of the marks obtained by three girls in a test was twice the average of the marks obtained by eight boys in that test. If the total marks obtained by all these examinees was 168, find the average marks each of the girls obtained ?

Pipes and Cistern

44 pipes can fill a large water tank in 27 hours. How many hours it take for 66 pipes to fill four such tanks ?

HCF and LCM

A natural number, when divided by 3, 4, 5, 6, and 7 respectively, leaves corresponding remainder of 2, 3, 4, 5 and 6. What is the smallest of all such numbers fulfilling the above condition ?

Coding-Decoding

If in a certain code language, PRINT is written as 34825 and TRUE is written as 5479. Then, how will TENURE be written in that language?

Order Sequence

Arrange the given words from smallest to biggest-
1.Jug
2.Mug
3.Bucket
4.Drum
5.Cup

Statement and Conclusion

Statements
All socks are shoes
Some shoes are black

Conclusions
I. Some shoes are socks.
II. No scoks is black

Numbers

The difference between the place value of 4 and 2 in the number 833749502 is ?

Analogy

GIKM : HJLN :: PRTV : .........?

Order Sequence

In a row of girls, Nanda is eighth from the left and Chanda is nineteenth from right. When Nanda and Chanda interchange their positions, Chanda becomes twnty-third form right. How many girls are there in the row?

Analogy

Summer: Day :: Winter : ........?

Bird:Winges :: Fish:........?