1. What is PL/SQL?
PL/SQL (Procedural Language/Structured Query Language) is Oracle’s procedural extension to SQL. It allows for programming constructs such as variables, loops, conditionals, and exception handling within SQL statements.

2. What are the key features of PL/SQL?
– It is tightly integrated with SQL and enables efficient data manipulation.
– It supports procedural constructs like loops, conditionals, and exception handling.
– It allows for the creation of reusable code blocks and functions.
– It offers strong error-handling capabilities.
– It provides support for cursors, triggers, and packages.

3. What is a PL/SQL block?
A PL/SQL block is a section of code that is enclosed within the keywords BEGIN and END. It can contain multiple statements and is used to group related operations together.

4. Explain the difference between a stored procedure and a function in PL/SQL.
– A stored procedure does not have a return value, whereas a function must return a value.
– Stored procedures are called using the EXECUTE or EXEC command, while functions can be used in queries like any other column or expression.
– Stored procedures can have output parameters, while functions can only return a single value.

5. What is a cursor in PL/SQL?
A cursor is a database object that allows the retrieval of data from a result set in a row-by-row fashion. It provides control over the processing of the result set and enables fetching, updating, and deleting records.

6. What is an exception in PL/SQL?
An exception is an error or an unexpected condition that occurs during the execution of a PL/SQL block. PL/SQL provides robust error-handling mechanisms to catch and handle such exceptions.

7. What is the difference between the EXCEPTION and WHEN OTHERS clauses?
The EXCEPTION clause is used to handle specific exceptions individually, while the WHEN OTHERS clause is used as a catch-all for any exception that is not explicitly handled. It is recommended to handle specific exceptions whenever possible for better control and error reporting.

8. How can you handle exceptions in PL/SQL?
Exceptions can be handled using the EXCEPTION block, which allows for individual handling of specific exceptions. By using appropriate keywords such as RAISE, EXCEPTION, and PRAGMA, exceptions can be caught, logged, and propagated as required.

9. What is a trigger in PL/SQL?
A trigger is a stored procedure that is automatically executed in response to a specific event, such as an insert, update, or delete operation on a table. Triggers can be used to enforce business rules, perform data validation, or audit changes.

10. What are packages in PL/SQL?
Packages are encapsulated units of code that can contain variables, constants, cursors, types, and subprograms. They provide a way to group related functionality together, making it easier to manage and reuse code.

11. Explain the difference between an inline view and a regular view in PL/SQL.
An inline view is a subquery that is used within a SQL statement, while a regular view is a named query stored in the database and can be accessed like a table. Inline views are not stored objects, and they exist only for the execution of the current query.

12. How can you pass parameters to a stored procedure or function?
Parameters can be passed to a stored procedure or function by specifying them in the procedure or function definition. The caller needs to provide values for these parameters when invoking the procedure or function.

13. What is the purpose of the %ROWTYPE attribute in PL/SQL?
The %ROWTYPE attribute allows us to declare variables that are compatible with a specific table or cursor record. It automatically maps the data type of each column in the record, making it useful for data manipulation.

14. What is the difference between a database trigger and a form trigger?
A database trigger is defined at the database level and is automatically fired in response to a specific database event. A form trigger, on the other hand, is defined within an Oracle Forms application and is fired based on specific user actions within the application.

15. How can you debug PL/SQL code?
PL/SQL code can be debugged using the DBMS_OUTPUT.PUT_LINE procedure to print messages, setting breakpoints using the DBMS_DEBUG package, or using an Integrated Development Environment (IDE) that supports PL/SQL debugging.

16. What is the purpose of the COMMIT statement in PL/SQL?
The COMMIT statement is used to permanently save changes made in a transaction. It ensures that all data modifications are written to disk and become permanent.

17. What is the purpose of the ROLLBACK statement in PL/SQL?
The ROLLBACK statement is used to undo changes made in a transaction. It reverts the database back to the state it was in before the transaction started.

18. What is the significance of the SAVEPOINT statement in PL/SQL?
The SAVEPOINT statement is used to mark a specific point within a transaction to which you can later roll back. It allows for partial rollback in case of errors or to achieve finer-grained control over undoing changes.

19. How can you optimize PL/SQL code?
PL/SQL code can be optimized by minimizing the number of database round trips, using bulk collect and FORALL statements for bulk data operations, avoiding excessive use of context switching between PL/SQL and SQL, and optimizing the use of indexes.

20. Explain implicit and explicit cursors in PL/SQL.
Implicit cursors are automatically created when a SQL statement is executed, such as in a SELECT INTO statement. Explicit cursors, on the other hand, are user-defined and can be explicitly declared, opened, fetched, and closed by the programmer for more control over the result set processing.

1. What is the difference between a package and a stored procedure?
A package is a collection of related procedures, functions, variables, and cursors grouped together. It provides a namespace to organize code and allows for better code reusability. On the other hand, a stored procedure is a standalone unit of code that performs a specific task.

2. How do you pass parameters to a PL/SQL stored procedure?
Parameters can be passed to a PL/SQL stored procedure by declaring them in the procedure signature and then using them within the procedure body. Parameters can be of IN, OUT, or IN OUT types.

3. Explain the difference between a function and a procedure in PL/SQL.
A function always returns a value, whereas a procedure may or may not return a value. Functions are used to compute and return a single value, while procedures are used to perform actions or tasks without returning a value.

4. What is an autonomous transaction in PL/SQL?
An autonomous transaction is an independent transaction that is initiated within another transaction. It allows you to perform separate commits or rollbacks inside the main transaction without affecting the main transaction’s outcome. It is useful in scenarios where you need to log changes or perform operations that are independent of the main transaction.

5. What are the benefits of using a cursor in PL/SQL?
Cursors are used in PL/SQL to retrieve multiple records from a result set. They provide better control and flexibility when dealing with complex queries and allow for processing data row by row. Cursors help reduce memory usage by fetching rows as needed instead of loading the entire result set into memory.

6. How do you handle exceptions in PL/SQL?
Exceptions in PL/SQL can be handled using the EXCEPTION block. The block is used to catch and handle any raised exceptions within the program. You can specify different exception handlers for specific types of exceptions to handle them appropriately.

7. What is a trigger in PL/SQL?
A trigger is a named PL/SQL block that is automatically executed in response to a specific database event, such as a DML operation or a system event. Triggers allow you to enforce business rules, perform validations, and automate certain actions.

8. How can you debug PL/SQL code?
PL/SQL code can be debugged using tools like Oracle SQL Developer or PL/SQL Developer. These tools provide features like breakpoints, step-by-step execution, variable inspection, and error logging to help identify and fix issues in the code.

9. What is the difference between a procedure and a function in PL/SQL?
A procedure is a named PL/SQL block that performs an action but does not return a value, while a function is a named PL/SQL block that computes and returns a single value. Procedures are used for actions and tasks, while functions are used for calculations and data manipulation.

10. How do you raise a user-defined exception in PL/SQL?
You can raise a user-defined exception in PL/SQL using the RAISE statement. The statement allows you to raise an exception explicitly based on a certain condition or business rule. You can also pass an error message along with the exception.

11. What is bulk binding in PL/SQL?
Bulk binding is a method used to improve performance by reducing context switches and reducing SQL statements needed to process large data sets. It involves binding multiple rows of data to a PL/SQL collection and performing operations on the collection instead of processing individual rows.

12. Explain the difference between a scalar and a composite data type.
A scalar data type represents a single value, such as a number, character, or date. Examples include NUMBER, VARCHAR2, and DATE. On the other hand, a composite data type represents a collection of values, such as a record or an array. Examples include RECORD, TABLE, and VARRAY.

13. How can you handle multiple exceptions in PL/SQL?
Multiple exceptions can be handled in PL/SQL using multiple EXCEPTION blocks or by using the EXCEPTION WHEN block. The EXCEPTION WHEN block allows you to specify different exception types and their corresponding handlers in a compact manner.

14. What is the role of a package in PL/SQL?
A package in PL/SQL encapsulates related procedures, functions, variables, and cursors into a single unit. It provides a way to organize code and improves code reusability. Packages can have public and private components, allowing better control over code visibility and accessibility.

15. What is the use of FORALL statement in PL/SQL?
The FORALL statement is used in PL/SQL to perform bulk operations on collections or tables. It allows you to process multiple elements of a collection or rows of a table at once, improving performance by reducing context switches.

16. Explain the difference between a PL/SQL table and a cursor.
A PL/SQL table is an array-like structure that holds a collection of elements of the same data type. It is used to hold temporary data for processing. On the other hand, a cursor is used to retrieve and process rows from a result set returned by a query. Cursors allow for row-by-row processing of data.

17. What is the purpose of using PRAGMA AUTONOMOUS_TRANSACTION in PL/SQL?
PRAGMA AUTONOMOUS_TRANSACTION is used to create an autonomous transaction within a PL/SQL block. It allows you to perform separate commits or rollbacks within the autonomous transaction, independent of the main transaction. This is useful when you need to update audit logs or perform operations that are not affected by the main transaction.

18. How can you improve the performance of PL/SQL code?
Performance of PL/SQL code can be improved by using appropriate indexing, minimizing context switches, using bulk processing techniques, optimizing queries, avoiding unnecessary variable declarations, and tuning SQL statements.

19. What is the purpose of the %ROWTYPE attribute in PL/SQL?
The %ROWTYPE attribute is used in PL/SQL to declare a variable that represents a complete row from a table or cursor. It allows you to fetch an entire row into a single variable, making it easier to work with and manipulate data.

20. Explain the difference between a local and global variable in PL/SQL.
A local variable is declared within a PL/SQL program block and exists only within that block’s scope. The variable is discarded when the block completes execution. On the other hand, a global variable is declared in a package or at the schema level and can be accessed by multiple program blocks within its scope. The variable retains its value until it is explicitly changed or the session ends.