Top 20 Oracle PL/SQL Interview Questions and Answers

Introduction

Databases store important business data. Orders. Customer records. Financial entries. Applications read and update this data every day. Many companies use the database platform from Oracle Corporation to manage these operations. To work with this database efficiently, developers use PL/SQL.

PL/SQL helps developers write stored procedures, functions, and triggers inside the database. These programs handle data validation, automation, and complex queries. During interviews, companies often test knowledge of these topics. Reading Oracle PL/SQL Interview Questions and Answers helps you review core concepts and prepare for technical discussions with more clarity.

List of Oracle PL/SQL Interview Questions for Freshers

• 1. What is Oracle PL/SQL?
• 2. What is the difference between SQL and PL/SQL?
• 3. Describe the basic PL/SQL structure.
• 4. What is a trigger in PL/SQL?
• 5. What are the uses of triggers?
• 6. What does the trigger’s WHEN clause mean?
• 7. When is it necessary to use a DECLARE block?
• 8. Why is WHERE CURRENT OF used in cursors?
• 9. What is a PL/SQL table?
• 10. Why is SYS.ALL_DEPENDENCIES used?
• 11. Make a distinction between the cursors listed in the package requirements and the ones listed in the procedures.
• 12. Define Join in PL/SQL.
• 13. What is a view?
• 14. What distinguishes the PL/SQL ROLLBACK FROM and ROLLBACK TO statements?
• 15. How can your PL/SQL code be debugged?

Oracle PL/SQL Technical Interview Questions and Answers for Freshers

1. What is Oracle PL/SQL?

Procedural languages like Oracle PL/SQL combine features from interactive SQL with procedural programming language characteristics like conditional branching and iteration.

2. What is the difference between SQL and PL/SQL?

• SQL is a language designed specifically for managing and modifying relational databases. Its main functions include searching through, adding, updating, and removing data from databases. 
• PL/SQL is a procedural language that builds upon SQL by incorporating loops, variables, and exception handling. Writing stored procedures, functions, and triggers in PL/SQL enables the creation of more intricate and reusable database logic.

3. Describe the basic PL/SQL structure.

The fundamental components of a PL/SQL block consist of:

The declaration section is where cursors, constants, and variables are defined.

The real PL/SQL code, including SQL statements and procedural logic, is written in the execution section.

Errors and exceptions that might arise during execution are handled under the exception handling section.

4. What is a trigger in PL/SQL?

A database object known as a trigger runs automatically in response to certain events on tables or views. It is used to apply the integrity constraint to database items. A database trigger is a PL/SQL software unit connected to a specific database table.

5. What are the uses of triggers?

Various uses of triggers include:

• Verify data changes
• Transparently record happenings
• Implement intricate corporate regulations.
• Continue to keep duplicate tables.
• Calculate the column values.
• Put in place intricate security authorizations

Every constant, variable, and parameter has a data type that determines its range of values and operations, format, and storage restrictions.

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6. What does the trigger’s WHEN clause mean?

The WHEN clause outlines the requirements under which the trigger must fire.

7. When is it necessary to use a DECLARE block?

Anonymous PL/SQL blocks, like non-stored and stand-alone procedures, employ this statement. The statement in the stand-alone file should be used first when using them.

8. Why is WHERE CURRENT OF used in cursors?

When referring to the current row using an explicit cursor, we utilize this clause. Without specifically mentioning the row ID, this clause permits applying modifications and deleting the row that is presently being considered.

Syntax:

UPDATE table_name SET field=new_value WHERE CURRENT OF cursor_name

9. What is a PL/SQL table?

All that exists between PL/SQL tables and database tables is an object of type table modeling. They are a means of offering arrays for quicker processing, which are essentially temporary tables in memory.

These tables facilitate the transfer of massive volumes of data, which helps to speed up the process.

10. Why is SYS.ALL_DEPENDENCIES used?

The SYS.ALL_DEPENDENCIES variable determines all of the dependencies of procedures, packages, triggers, and functions that are available to the current user. 

Name, dependency_type, type, referenced_owner, and other columns are returned.

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11. Make a distinction between the cursors listed in the package requirements and the ones listed in the procedures.

• Since they have a local scope, the cursors specified in the procedures cannot be used by other procedures.
• Other methods can utilize and access the cursors that are defined in package specifications since they are handled with a global scope.

12. Define Join in PL/SQL.

Combining rows from two or more tables, views, or materialized views is known as a join query. When a query has more than one table in the FROM clause, the Oracle Database does a join. A join condition is present in the FROM or WHERE clause of the majority of these queries.

13. What is a view?

One or more tables can be joined to form a view. It is a virtual table with rows and columns, just like a real table, that is based on the result set of a SQL query. The construct VIEW statement can be used to construct a view.

14. What distinguishes the PL/SQL ROLLBACK FROM and ROLLBACK TO statements?

• To undo every modification made since the start of the transaction, use the ROLLBACK command.
• The transaction may only be undone up to a SAVEPOINT using the ROLLBACK TO command. The transaction is still ongoing even before the command is given because it cannot be turned back before the SAVEPOINT.

15. How can your PL/SQL code be debugged?

• To debug our code, we can use the DBMS_OUTPUT and DBMS_DEBUG statements:
• The output is printed to the standard console via DBMS_OUTPUT.
• The output is printed to the log file by DBMS_DEBUG.

List of Oracle PL/SQL Interview Questions for Freshers

• 11. Describe the role of an Oracle PL/SQL index.
• 12. What characterizes an Oracle PL/SQL view?
• 13. How does Oracle PL/SQL handle NULL values during comparisons and arithmetic operations?
• 14. Distinguish between a stored procedure and a function in Oracle PL/SQL.
• 15. How does Oracle PL/SQL manage transactions?
• 16. Explain the utility of the HAVING clause in SQL.
• 17. Describe the importance of database constraints in Oracle PL/SQL.
• 18. How does Oracle PL/SQL manage transactions?
• 19. Explain the utility of the HAVING clause in SQL.
• 20. Describe the importance of database constraints in Oracle PL/SQL.
• 21. Explain Nested Table in Oracle PL/SQL.

Oracle PL/SQL Technical Interview Questions and Answers for Experienced

11. Describe the role of an Oracle PL/SQL index.

An Oracle PL/SQL index acts as a database construct utilized to expedite data retrieval by offering rapid access to rows based on the values stored in indexed columns. It optimizes query performance by minimizing the number of data blocks that necessitate scanning.

12. What characterizes an Oracle PL/SQL view?

An Oracle PL/SQL view constitutes a virtual table formulated through a query. While it mirrors the structure of a table with rows and columns, it does not store data. Views afford a means to present data from one or more tables in a customized format sans altering the underlying tables’ structure.

13. How does Oracle PL/SQL handle NULL values during comparisons and arithmetic operations?

In Oracle PL/SQL, NULL symbolizes the absence of a value. Consequently, comparisons involving NULL typically yield NULL outcomes, and arithmetic operations with NULL operands similarly result in NULL unless explicitly managed using functions such as NVL or COALESCE.

14. Distinguish between a stored procedure and a function in Oracle PL/SQL.

• A stored procedure comprises precompiled SQL statements stored in the database, executed as a unified unit.
• Conversely, a function is a database object returning a single value based on input parameters and executing a specific task.

15. How does Oracle PL/SQL manage transactions?

• Oracle PL/SQL employs transactions to ensure data integrity and consistency within the database.
• Transactions encompass SQL statements treated as a single logical unit, enabling adherence to ACID properties.

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16. Explain the utility of the HAVING clause in SQL.

• The HAVING clause filters grouped rows following a GROUP BY operation based on specified conditions.
• It enables condition applications to aggregate data, extending filtering capabilities beyond the WHERE clause.

17. Describe the importance of database constraints in Oracle PL/SQL.

• Database constraints are regulations imposed on tables to enforce data integrity and consistency.
• They establish data storage restrictions, ensuring compliance with predefined rules and preventing insertion of invalid or inconsistent data.

18. How does Oracle PL/SQL manage transactions?

• Oracle PL/SQL employs transactions to ensure data integrity and consistency within the database.
• Transactions encompass SQL statements treated as a single logical unit, enabling adherence to ACID properties.

19. Explain the utility of the HAVING clause in SQL.

• The HAVING clause filters grouped rows following a GROUP BY operation based on specified conditions.
• It enables condition applications to aggregate data, extending filtering capabilities beyond the WHERE clause.

20. Describe the importance of database constraints in Oracle PL/SQL.

• Database constraints are regulations imposed on tables to enforce data integrity and consistency.
• They establish data storage restrictions, ensuring compliance with predefined rules and preventing insertion of invalid or inconsistent data.

21. Explain Nested Table in Oracle PL/SQL.

In Oracle PL/SQL, a nested table serves as a datatype employed for housing collections of elements within a column of a database table. Unlike conventional tables storing rows of data, nested tables accommodate multiple rows within each cell of a column. These collections may vary in length and can encompass any data type supported by Oracle PL/SQL, spanning scalar types, nested tables, or user-defined types. This setup offers a versatile means to depict and administer intricate, hierarchical data structures within a relational database.

Conclusion

You reached the end of these Oracle PL/SQL Interview Questions and Answers. Use them as a quick revision before your interview. Read the questions. Try to answer them on your own. Then check the explanation.

Spend time writing small PL/SQL programs. Practice procedures. Test simple triggers. Work with sample tables. This habit improves clarity during technical discussions.

If you want guided practice, consider Oracle PL/SQL Training in Chennai at Softlogic Systems. The program gives hands on database exercises and helps you prepare for Oracle related roles.