pl sql interview questions

Top PL/SQL Interview Questions: Ace Your Database Development Interview

Introduction:
PL/SQL (Procedural Language/Structured Query Language) is a powerful programming language used for managing and manipulating data in Oracle databases. If you’re preparing for a PL/SQL interview, it’s essential to familiarize yourself with common interview questions to demonstrate your expertise in this domain. In this blog post, we will explore some of the top PL/SQL interview questions and provide detailed answers to help you succeed in your interview.

1. What is PL/SQL, and what are its advantages?
PL/SQL is a procedural extension of SQL that allows you to write powerful database-driven applications. Its advantages include:

a) Integration with SQL: PL/SQL seamlessly integrates with SQL, allowing for efficient data manipulation and retrieval.

b) Procedural Capabilities: PL/SQL supports loops, conditions, and exception handling, enabling complex program logic to be implemented in the database.

c) Improved Performance: PL/SQL can execute multiple SQL statements as a single block, reducing network traffic and enhancing performance.

2. What are the different types of PL/SQL blocks?
PL/SQL blocks are the basic units of code in PL/SQL. There are three types of PL/SQL blocks:

a) Anonymous Blocks: These are unnamed blocks of PL/SQL code that are not stored in the database and can be executed directly.

b) Named Blocks: These are named PL/SQL blocks that are stored in the database as stored procedures, functions, or triggers.

c) Nested Blocks: PL/SQL allows blocks to be nested within other blocks. This feature enables modularity and reusability of code.

3. Differentiate between a stored procedure and a stored function.
Stored Procedure:
– A stored procedure does not return a value directly.
– It can have both input and output parameters.
– It can execute multiple SQL statements.
– It is invoked using the EXECUTE or CALL statement.

Stored Function:
– A stored function always returns a single value.
– It can have both input and output parameters.
– It can execute SQL statements but cannot execute DDL statements.
– It is invoked in SQL statements or within other PL/SQL blocks.

4. What is the difference between TRUNCATE and DELETE statements?
TRUNCATE and DELETE are SQL statements used to remove data from a table, but they differ in functionality:

TRUNCATE:
– Removes all rows from a table.
– Resets the high water mark.
– Commits after the operation.
– Cannot be rolled back.
– Does not generate any triggers.

DELETE:
– Removes specific rows based on the condition.
– Retains the high water mark.
– Can be rolled back.
– Triggers can be fired before and after the operation.

5. Explain the difference between EXCEPTION and RAISE_APPLICATION_ERROR.
EXCEPTION:
– EXCEPTION is a predefined exception handler in PL/SQL.
– It handles predefined and user-defined exceptions.
– It can be used within an exception handling block to catch and handle exceptions.

RAISE_APPLICATION_ERROR:
– RAISE_APPLICATION_ERROR is a procedure used to raise user-defined exceptions.
– It allows you to define custom error messages and error numbers.
– It can be used to propagate errors to the calling environment.

Conclusion:
Preparing for a PL/SQL interview requires a solid understanding of the language’s fundamental concepts and features. By reviewing and practicing common interview questions like the ones discussed in this blog post, you’ll be better equipped to showcase your PL/SQL expertise. Remember to adapt your answers to reflect your own experience and ensure a confident and concise delivery during the interview. Good luck!

 

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