1. What is PL/SQL?
PL/SQL stands for Procedural Language/Structured Query Language. It is Oracle’s extension to SQL that allows you to write full-featured programs using procedural constructs.

2. What are the advantages of using PL/SQL?
Some advantages of using PL/SQL include:
– Improved performance by consolidating multiple SQL statements into a single block.
– Increased productivity through the use of looping structures and conditional statements.
– Enhanced security by allowing code to run on the database server instead of the client.

3. What is a PL/SQL block?
A PL/SQL block is the basic unit of code in PL/SQL. It consists of a declaration section, an executable section, and an exception handling section. It is enclosed between the keywords BEGIN and END.

4. What are cursors in PL/SQL?
A cursor is a named private SQL area used to process rows returned by a SQL statement. It allows you to retrieve multiple rows from a query and process them one at a time.

5. What is the difference between a cursor and a cursor variable?
A cursor is a named private SQL area, whereas a cursor variable is a PL/SQL variable that points to a cursor. A cursor can be explicit or implicit, while a cursor variable is always explicit.

6. What are the different types of loops available in PL/SQL?
PL/SQL provides three types of loops:
– FOR loop: Executes a sequence of statements a specified number of times.
– WHILE loop: Executes a sequence of statements while a condition is true.
– LOOP loop: Repeats a sequence of statements until an exit condition is met.

7. What are exceptions in PL/SQL?
Exceptions are events that disrupt the normal flow of control in a PL/SQL block. They are used to handle errors and provide customized error messages to the user.

8. How do you handle exceptions in PL/SQL?
Exceptions in PL/SQL are handled using the built-in exception handling block, which consists of the keywords EXCEPTION, WHEN, and THEN. You can catch and handle specific exceptions or use a generic handler to catch all exceptions.

9. What is a trigger in PL/SQL?
A trigger is a stored PL/SQL block associated with a specific table or view. It automatically executes in response to specified events, such as inserting, updating, or deleting data.

10. What are the different types of triggers in PL/SQL?
There are four types of triggers in PL/SQL:
– DML triggers: Fired in response to DML statements (INSERT, UPDATE, DELETE).
– Instead-of triggers: Used to override the default behavior of a view.
– System triggers: Fired by system events, such as startup or shutdown.
– Compound triggers: Introduced in Oracle 11g, they are a combination of statement-level and row-level triggers.

11. How do you debug PL/SQL code?
PL/SQL provides several methods for debugging code, such as using the DBMS_OUTPUT.PUT_LINE procedure to display output, the DBMS_DEBUG package for more advanced debugging, or using debuggers provided by integrated development environments (IDEs).

12. What are packages in PL/SQL?
A package is a collection of related procedures, functions, variables, and cursors grouped together as a single program unit. It provides a way to encapsulate and modularize code for better organization and reusability.

13. What is the difference between a procedure and a function?
A procedure in PL/SQL is a named block that performs one or more actions and does not return a value. A function, on the other hand, returns a value and can be used in SQL statements.

14. What is data binding in PL/SQL?
Data binding in PL/SQL refers to the process of associating a variable or parameter with a database column or expression. It allows you to pass values between SQL and PL/SQL statements.

15. What is the difference between a scalar variable and a record variable?
A scalar variable holds a single value of a predefined type, such as a number or string. A record variable, on the other hand, can hold multiple values of different types from a specific table or query result set.

16. What is the purpose of using BULK COLLECT in PL/SQL?
The BULK COLLECT statement is used to fetch multiple rows from the database into a collection variable in a single operation. It improves performance by reducing context switches between the PL/SQL and SQL engines.

17. How do you create a function-based index in PL/SQL?
To create a function-based index in PL/SQL, you use the CREATE INDEX statement with the keyword FUNCTION-BASED followed by the indexed expression or function.

18. What is the purpose of the %ROWCOUNT attribute in PL/SQL?
The %ROWCOUNT attribute returns the number of rows affected by the most recent SQL statement. It is often used in loops to control processing or to display feedback to the user.

19. What is the difference between an anonymous PL/SQL block and a stored procedure?
An anonymous PL/SQL block is a one-time, ad hoc block of code that is not stored in the database, while a stored procedure is a named object that is compiled and stored in the database for repeated use.

20. How do you use dynamic SQL in PL/SQL?
Dynamic SQL is a technique that allows you to construct and execute SQL statements dynamically at runtime. It is achieved using the EXECUTE IMMEDIATE statement or the DBMS_SQL package.

1. What is the difference between a stored procedure and a function?
A stored procedure does not return a value, while a function always returns a value.

2. How do you handle exceptions in PL/SQL?
Exceptions in PL/SQL can be handled using the BEGIN … EXCEPTION … END block or by using the EXCEPTION block in a stored procedure or function.

3. What is the difference between a cursor and a cursor variable?
A cursor is a named memory area used to store query results, while a cursor variable is a reference to a cursor.

4. How do you handle NULL values in PL/SQL?
To handle NULL values, you can use the IS NULL condition in an IF statement or use the NVL function to replace NULL values with a default value.

5. What is bulk binding in PL/SQL?
Bulk binding is a method that allows you to bind multiple rows to a PL/SQL collection at once, improving performance compared to row-by-row processing.

6. What is the difference between a database trigger and a stored procedure?
A database trigger is automatically executed when a specific event occurs in the database, while a stored procedure needs to be explicitly called by a user.

7. What is the purpose of the COMMIT statement in PL/SQL?
The COMMIT statement is used to save any changes made during the transaction and make them permanent. It ensures data integrity.

8. What is the difference between a global and a local temporary table?
A global temporary table is shared among all users of a database and exists until the session ends, while a local temporary table is specific to a user’s session and ceases to exist at the end of the session.

9. What are autonomous transactions in PL/SQL, and how are they useful?
Autonomous transactions allow you to perform separate independent transactions within a larger transaction. They are useful for logging and error handling purposes.

10. How do you optimize PL/SQL performance?
Some techniques to optimize PL/SQL performance include using bulk operations, minimizing context switches, using proper indexing, and optimizing SQL queries.

11. What are the benefits of using PL/SQL in Oracle?
PL/SQL provides tight integration with the Oracle database and offers advantages such as improved performance, better security, and easier maintenance of SQL code.

12. What is the purpose of the FORALL statement?
The FORALL statement is used to perform bulk SQL operations on collections. It improves performance by reducing the number of context switches between PL/SQL and SQL engines.

13. How can you handle large amounts of data in PL/SQL?
For handling large data sets, you can use features such as bulk binding, cursors, and perform data operations in smaller, manageable chunks.

14. What is the role of packages in PL/SQL?
Packages in PL/SQL allow you to encapsulate related procedures, functions, variables, and cursors, providing modularity and reusability in your code.

15. How do you measure the performance of a PL/SQL code?
PL/SQL performance can be measured using tools such as Oracle Enterprise Manager, SQL Trace, and SQL Developer’s performance tuning features.

16. How can you raise a custom exception in PL/SQL?
You can use the RAISE_APPLICATION_ERROR procedure to raise a custom exception in PL/SQL, specifying an error code and message.

17. What is the purpose of the PRAGMA EXCEPTION_INIT statement?
The PRAGMA EXCEPTION_INIT statement associates a specific exception with an error code, allowing you to handle the exception in a more controlled manner.

18. How do you use PL/SQL table types?
PL/SQL table types allow you to create arrays of data within a PL/SQL program. You can use them to store and manipulate data efficiently.

19. Explain the difference between a trigger and a constraint.
A trigger is a piece of code that executes in response to a specific event, while a constraint is a rule defined on a table to maintain data integrity.

20. How do you debug PL/SQL code?
PL/SQL code can be debugged using tools such as Oracle SQL Developer, which provides features like breakpoints, watch expressions, and stepping-through code execution.