Oracle PL/SQL Interview Questions and Answers

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.
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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 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.

What is Raise_application_error?
Raise_application_error is a procedure of package DBMS_STANDARD which allows to issue a user_defined error messages from stored sub-program or database trigger.
What is Pragma EXECPTION_INIT? Explain the usage?

he PRAGMA EXECPTION_INIT tells the complier to associate an exception with an oracle error. 
E.g. PRAGMA EXCEPTION_INIT (exception name, oracle error number)

What are SQLCODE and SQLERRM and why are they important for PL/SQL developers?

SQLCODE returns the value of the error number for the last error encountered. 

SQLERRM returns the actual error message for the last error encountered. They can be used in exception handling to report, or, store in an error log table, the error that occurred in the code.

What is a package spec and package body? Why the separation?

Spec declares public constructs. Body defines public constructs, additionally declares and defines Private constructs.
Separation helps make development easier. Dependency is simplified. You can modify body without invalidating dependent objects.

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In which year was the battle of ‘Koregaon Bhima’ fought?

The approach that is very useful in organizing the content in history is.

General Knowledge of India

NITI Aayog stands for _____.

General Knowledge of MP

India’s first Ramayan art museum was established at?

Errors Identification

Read the sentence carefully and choose the option that has an error in it:
The management’s trusted employee was suspected of stealing large sum of money.

Read the sentence carefully and choose the option that has an error in it:
The teacher asked the child to repeat again because he spoke feebly.

Fill in the blank

Fill in the blank with the most appropriate preposition in the given sentence.
Let’s sit _________ the shade of this beautiful tree.

Choose the most appropriate determiner for the given sentence.
________of what he said was very sensible.

Substitution

Choose the option that substitutes the given phrase appropriately.
A work of art made by carving

Correct sentence

Choose the option that best transforms the sentence into its Indirect form:
‘What country do you come from?’ said the police officer.

Alternative Phrase

Choose the option that best explains the highlighted expression:
All human beings have feet of clay.

Fill in the blank

Choose an appropriate modal for the given sentence:
My doctor said that I_____ stop smoking as one of my lungs got infected.

Choose the appropriate prepositions for the given sentence:
My parents have been married ________ forty-nine years, but you can still see the love ________ their eyes.

Choose the appropriate conjunction for the given sentence:
______ it rains, the college will declare the holiday.

Antonyms

Choose the appropriate antonym for the highlighted word in the given sentence.
The family protracted their visit by several days.

Tenses

Choose the appropriate tenses to fill in the blanks in the given sentence:
Please _________ a noise. Ritu __________ to sleep.

Synonyms

Choose the appropriate synonym for the highlighted word in the given sentence.
Does he really expect us to believe such a flimsy excuse?

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