Oracle Quiz - MCQ - Multiple Choice Questions

Oracle Database, often simply referred to as Oracle, is one of the most widely used relational database management systems (RDBMS) in the world. Its robust features and scalability make it a favorite choice for enterprises. If you're a beginner aiming to test your foundational understanding of Oracle, this quiz will be a valuable resource. Dive in and test your knowledge!

Note that each question is followed by the correct answer and an explanation to help reinforce your knowledge.

1. What does RDBMS stand for?

A. Relational Database Management System

B. Rational Database Management System

C. Random Database Measurement System

D. Rational Database Measurement System

Answer:

A. Relational Database Management System

Explanation:

RDBMS stands for Relational Database Management System, emphasizing the relational nature of the data.

2. Which SQL command is used to retrieve data from a database in Oracle?

A. GET

B. FETCH

C. SELECT

D. RETRIEVE

Answer:

C. SELECT

Explanation:

The SELECT command is used to query and retrieve data from a database table.

3. Which Oracle feature ensures that the data remains consistent even after a system failure?

A. Redundancy

B. Replication

C. Atomicity

D. Backup

Answer:

C. Atomicity

Explanation:

Atomicity is one of the ACID properties, ensuring that all operations in a transaction are completed successfully or none at all, ensuring data consistency.

4. Which clause is used in conjunction with the SELECT statement to filter results?

A. SORT BY

B. LIMIT

C. WHERE

D. FILTER

Answer:

C. WHERE

Explanation:

The WHERE clause is used with the SELECT statement to filter the query results based on specified conditions.

5. Which Oracle SQL function returns the current date and time?

A. GET_DATE

B. CURRENT_DATE

C. NOW

D. TODAY

Answer:

B. CURRENT_DATE

Explanation:

CURRENT_DATE returns the current date in Oracle SQL.

6. Which Oracle clause allows you to sort the results of a SELECT query?

A. SORT BY

B. ORDER BY

C. ALIGN BY

D. GROUP BY

Answer:

B. ORDER BY

Explanation:

The ORDER BY clause is used to sort the results of a SELECT query in ascending or descending order based on one or more columns.

7. Which data type in Oracle is used to store large blocks of text?

A. CHAR

B. STRING

C. TEXT

D. CLOB

Answer:

D. CLOB

Explanation:

CLOB (Character Large Object) is used to store large blocks of text data in Oracle.

8. What is the maximum size of a VARCHAR2 in Oracle?

A. 2000 bytes

B. 4000 bytes

C. 8000 bytes

D. 16000 bytes

Answer:

B. 4000 bytes

Explanation:

The maximum size of a VARCHAR2 in Oracle is 4000 bytes.

9. In Oracle, which command is used to remove a table from the database?

A. DELETE TABLE

B. REMOVE TABLE

C. DROP TABLE

D. DISCARD TABLE

Answer:

C. DROP TABLE

Explanation:

The DROP TABLE command is used to remove an existing table from the Oracle database.

10. Which keyword is used to create a unique constraint on a column in Oracle?

A. UNIQUE

B. DISTINCT

C. ONLY

D. SPECIAL

Answer:

A. UNIQUE

Explanation:

The UNIQUE keyword is used to ensure that all values in a column are distinct.

11. Which Oracle command is used to apply changes of a transaction permanently to the database?

A. COMMIT

B. SAVE

C. APPLY

D. CONFIRM

Answer:

A. COMMIT

Explanation:

The COMMIT command is used to permanently save all the changes made during the current transaction.

12. What is the primary purpose of a primary key in an Oracle table?

A. To enhance the performance of the table

B. To ensure unique values in a column

C. To create relationships with other tables

D. To automatically increment values

Answer:

B. To ensure unique values in a column

Explanation:

A primary key's main purpose is to ensure unique values for a column and identify each record uniquely in a table.

13. Which Oracle clause would you use to retrieve distinct values from a column?

A. UNIQUE

B. DISTINCT

C. SPECIAL

D. ONLY

Answer:

B. DISTINCT

Explanation:

The DISTINCT keyword is used with the SELECT statement to fetch unique values from a column.

14. In Oracle, which command would you use to modify an existing table structure?

A. MODIFY TABLE

B. CHANGE TABLE

C. ALTER TABLE

D. ADJUST TABLE

Answer:

C. ALTER TABLE

Explanation:

The ALTER TABLE command is used to make changes to an existing table structure, such as adding or deleting columns.

15. What does PL/SQL stand for in Oracle?

A. Procedural Language/Structured Query Language

B. Programming Language/SQL

C. Processed Logic/SQL

D. Protocol Language/SQL

Answer:

A. Procedural Language/Structured Query Language

Explanation:

PL/SQL stands for Procedural Language/Structured Query Language, and it's Oracle's procedural extension to SQL.

16. What does the Oracle SYSDATE function return?

A. The system's date and time

B. Only the system's date

C. Only the system's time

D. The start date of the system

Answer:

A. The system's date and time

Explanation:

The SYSDATE function in Oracle returns the current date and time of the system.

17. Which Oracle feature helps in recovering the database to a previous state without using backups?

A. Flashback

B. Rollback

C. Restore Point

D. Recovery Point

Answer:

A. Flashback

Explanation:

The Flashback feature in Oracle allows you to recover the database to a previous state without the need for traditional point-in-time recovery methods.

18. Which Oracle SQL function returns the first non-null value in a list?

A. NVL()

B. COALESCE()

C. NULLIF()

D. ISNULL()

Answer:

B. COALESCE()

Explanation:

The COALESCE() function returns the first non-null value from a list of expressions.

19. Which Oracle clause aggregates data returned from a query into subgroups?

A. ORDER BY

B. ALIGN BY

C. SORT BY

D. GROUP BY

Answer:

D. GROUP BY

Explanation:

The GROUP BY clause is used in Oracle SQL to aggregate data into subgroups based on columns.

20. Which Oracle command is used to reverse the changes of a transaction before it's been committed?

A. REVERT

B. UNDO

C. ROLLBACK

D. RESET

Answer:

C. ROLLBACK

Explanation:

The ROLLBACK command is used to reverse the changes made during the current transaction that have not been permanently saved to the database.

21. Which Oracle feature allows a column's value to be automatically incremented with each new record insertion?

A. Auto-fill

B. Auto-increment

C. Sequence

D. Increment-by-one

Answer:

C. Sequence

Explanation:

In Oracle, the SEQUENCE is used to generate a series of unique numbers for primary keys automatically.

22. Which command removes all records from a table but retains the table structure in Oracle?

A. DELETE

B. REMOVE

C. EMPTY

D. TRUNCATE

Answer:

D. TRUNCATE

Explanation:

The TRUNCATE command is used to remove all records from a table but it does not delete the table structure.

23. Which of the following SQL clauses is used to provide a substitute value for NULL?

A. DEFAULT

B. SUBSTITUTE

C. NVL

D. COALESCE

Answer:

C. NVL

Explanation:

The NVL function in Oracle is used to replace NULL values with another value.

24. What is the primary difference between an INNER JOIN and an OUTER JOIN in Oracle?

A. INNER JOIN returns only the rows when there is a match in both tables, while OUTER JOIN returns all rows from one table and the matching rows from another.

B. INNER JOIN returns all rows from both tables, while OUTER JOIN returns only the rows where there is a match.

C. There is no difference; both are the same.

D. INNER JOIN uses indexes while OUTER JOIN does not.

Answer:

A. INNER JOIN returns only the rows when there is a match in both tables, while OUTER JOIN returns all rows from one table and the matching rows from another.

Explanation:

The primary difference between INNER JOIN and OUTER JOIN is how they handle non-matching rows.

25. Which Oracle SQL function returns the number of characters in a string?

A. CHAR_COUNT

B. COUNT

C. LENGTH

D. NUM_CHARS

Answer:

C. LENGTH

Explanation:

The LENGTH function in Oracle returns the number of characters in a string.

26. In Oracle, a logical unit of work is defined by which of the following?

A. Session

B. Transaction

C. Instance

D. Process

Answer:

B. Transaction

Explanation:

In Oracle, a transaction represents a logical unit of work that may consist of one or more SQL statements.

27. Which Oracle feature provides a real-time, memory-resident database, which maximizes performance by eliminating disk I/O?

A. Oracle Real-Time Database

B. Oracle In-Memory

C. Oracle Flash

D. Oracle QuickDB

Answer:

B. Oracle In-Memory

Explanation:

Oracle In-Memory provides a real-time, memory-resident database for improved performance.

28. In Oracle SQL, what is the result of the following expression: SELECT ROUND(50.456, 1) FROM DUAL;?

A. 50.4

B. 50.5

C. 50.46

D. 50.46

Answer:

B. 50.5

Explanation:

The ROUND function rounds the number to the specified number of decimal places. In this case, it rounds to one decimal place, so 50.456 becomes 50.5.

29. Which type of index in Oracle uses a bitmap to indicate the row locations?

A. Primary Index

B. Bitmap Index

C. B-tree Index

D. Spatial Index

Answer:

B. Bitmap Index

Explanation:

Bitmap Index uses a bitmap for each key value and includes pointers to the rows having that value.

30. Which command in Oracle is used to remove a stored procedure?

A. REMOVE PROCEDURE

B. DELETE PROCEDURE

C. DROP PROCEDURE

D. DESTROY PROCEDURE

Answer:

C. DROP PROCEDURE

Explanation:

The DROP PROCEDURE command is used to remove a stored procedure from the database.