Top Oracle Interview Questions and Answers

Overview of the Interview Process

According to Oracle's hiring team, to truly build for everyone, a diversity of perspectives and experiences and a fair hiring process is the first step in getting there.

 

 

Here is the interview process conducted by Oracle to hire a capable workforce for themselves. Oracle interview experience is different for different individuals. But there is a typical pattern that is followed for the selection of workforce at Oracle.

Oracle Interview Process:

Resume Screening: The first step in Oracle’s hiring process is the thorough screening of resumes. The Oracle hiring team is searching for specialized knowledge, such as technical proficiency and relevant experience, and additionally educational credentials. 

Online Coding Round: Following resume screening, an online exam round is held with multiple-choice questions covering topics like data structures and algorithms, networking, object-oriented programming, database management systems, logical reasoning, and quantitative analysis.

Technical Interview Round 1:In the Technical Interview Round, a video or phone call is scheduled with the candidate, and his coding skills are assessed. The interviewer generally asks two questions to the candidate based on Data Structures and Algorithms.

Technical Interview Round 2:This is a personal interview round where tricky and complex questions based on data structures are asked. Questions related to the candidate's CV may also be asked in this round.

Also, some interviewers like to ask for puzzles to test the thinking ability of the candidate.

HR Round: This is an informal round where the interviewer can ask general questions about the candidate's work experience and ethics-related inquiries. This helps the company to decide whether the applicant is a cultural fit for their company. 

Final Interview: Technical and behavioral tests are combined in the final round. It frequently consists of a final assessment of the applicant's work history, ethical considerations, and fit with the company culture.

Basic Oracle Interview Questions

1) What is the difference between varchar and varchar2 data types?

VARCHAR2 is the recommended data type in Oracle for variable-length character data, with a limit of 4000 bytes. VARCHAR is reserved for future use, and while they behave the same now, it may change in future Oracle releases. Neither occupies space for NULL values, but Oracle advises using VARCHAR2 for reliability.

2) In which language has Oracle been developed?

Oracle has been developed using C Language. Some parts of it also utilize C++ for specific functionalities.

3) What is a RAW datatype?

The RAW datatype in Oracle stores data in binary format. The maximum size for a RAW column in a table is 2000 bytes, while for RAW variables in PL/SQL, the limit is 32767 bytes.

4) What is the use of the NVL function?

The NVL function replaces NULL values with another or given value. Example is –

NVL (Value, replace value) returns replace_value if the value is NULL; otherwise, it returns a value.

5) Whether any commands are used for Month calculation? If so, what are they?

In Oracle, the MONTHS_BETWEEN function is used to find the number of months between the given dates. Example is –

MONTHS_BETWEEN (Date 1, Date 2) returns the difference in months between date 1 and date 2.

The questions mentioned above were some of the general questions related to Oracle, and they are not restricted by categories.

6) What are Indexes in Oracle? 

Indexes are database objects created to improve query performance by providing faster access to data. They allow the database to find rows more quickly in large tables.

7) What are Schema Objects?

Schema objects are logical structures that store or manipulate data within an Oracle database, owned by specific users. It includes 

- Tables 

- Views 

- Indexes

- Procedures

8) What is the NULL value in Oracle?

Unknown or missing data is indicated by a NULL value.

9)What is Oracle RAC (Real Application Clusters)?

Oracle RAC allows multiple computers to run Oracle RDBMS software simultaneously while accessing a single database, providing high availability and scalability for database systems.

10) What is PL/SQL?

Oracle uses PL/SQL, which is an extension of SQL. PL/SQL generates more potent SQL queries by fusing the processing power of procedural languages with SQL's data manipulation capabilities. It tells the compiler what to do using SQL and how to do it using a procedural method.

11) What is a View in Oracle? 

A view in Oracle is a virtual table created by a SQL query that selects data from one or more tables. It does not store data itself but displays data from the underlying tables.

12) What is the difference between DELETE and TRUNCATE commands in Oracle? 

The DELETE command removes specific rows from a table and can be rolled back. The TRUNCATE command removes all rows from a table without the ability to roll back, and it is faster than DELETE because it does not log individual row deletions.

Oracle Interview Questions for Beginners

Oracle interview questions for freshers are the typical questions that are asked in all companies. Here are some of them:

13) What do you know about our company?

This question is generally asked by the interviewer or hiring manager at the beginning of the conversation to know how much you are aware of the organization where you want to work.

The best way to tackle this interview question is to research the company where you will face the interview.

Read online about the company's latest updates, understand its business, and thoroughly read the job description.

14) How did you hear about this job?

The interviewer asks this question to see the candidate's interest in the company and job profile. Generally, the candidates answer this question by saying I have got the notification through some job portal or website where I have applied.

I also desire to work for this company, so I have checked its official website, where I see the job openings, and I am here. If you know any company employee who has advised you to apply to this company, this would be a good time to mention their name.

15) Why do you want to work here? / Why do you want to work with this company?

This is a general interview question that companies ask fresher to know what they want and how much they know about the company they are applying for.

Before appearing for the interview, the candidates are always recommended to study and learn about the company's background, values, operations, services, and other vital details.

16) What are the primary responsibilities of an Oracle DBA?

An Oracle DBA is responsible for the installation, configuration, performance tuning, backup, recovery, and security of the Oracle Database.

17) What is the use of the PRIMARY KEY constraint in Oracle?

Each row in a database table is uniquely identified by the PRIMARY KEY constraint, which also makes sure that no two rows have the same key values.

18) How can you optimize query performance in Oracle? 

Indexing, rewriting complex queries, avoiding full table scans, partitioning large tables, and making effective use of Oracle hints are all ways to optimize queries in Oracle.

 

 

Oracle Interview Questions for Experienced Professionals

19) What are the different types of modules associated with Oracle forms?

The different types of modules associated with Oracle forms include:

- Form module

- Menu module

- Object Library module

- PL/SQL Library module

20) Which are the fundamental types of Joins used in Oracle to write subqueries?

For experienced candidates, this is one of the most common Oracle interview questions. Subqueries in the Oracle database are written using the following primary join types:

- Self Join

- Equi Join

- Outer Join

21) Explain the use of the Control File in Oracle.

The Control file in the Oracle database is used to identify log files that need to be opened for certain database operations to occur. The control file helps manage critical information needed for database operations, including database consistency and recovery.

22) What are Actual and Formal Parameters?

Expressions and variables referenced in the parameter list of a subprogram are called Actual Parameters.

Variables that are declared within the body of the subprogram are known as Formal Parameters.

23) What are the different types of database objects in Oracle?

There are fundamentally five different types of database objects that include:

- Tables

- Views Indexes

- Tablespaces

- Indexes

- Synonyms

24) How do you troubleshoot performance issues in an Oracle database?

Analyze AWR (Automatic Workload Repository) reports, SQL execution plans, and system resource utilization (CPU, memory, I/O) to find bottlenecks and troubleshoot Oracle database performance issues. Next, optimize database configurations, indexing, and inefficient SQL queries.

25) How do you configure Oracle Grid Infrastructure?

To configure Oracle Grid Infrastructure, you install the Grid Infrastructure software, set up Oracle ASM (Automatic Storage Management), and configure Oracle Clusterware for high availability. This process involves running the Oracle Universal Installer (OUI) and using the Grid Setup Wizard for cluster configuration.

Oracle Technical Interview Questions

Some of the questions for highly skilled people in the industry:

26) List the various components of the physical database structure of an Oracle database.

The different components of the physical database structure of an Oracle database are listed down below: -

- Greater than equal to two redo log files.

- Greater than equal to one data file.

- Greater than equal to one control file.

27) Define a tablespace in context with the Oracle database.

The Logical Storage Unit of an Oracle database is called a tablespace. It is nothing but a set of related logical structures.

Tablespace groups relate the analytical systems of the database together. Logically, the data is stored in the tablespaces in Oracle, and physically, the information is stored in the data files associated with the respective tablespaces.

28) What are the different types of backups in Oracle?

There are two main types of backups in Oracle:

- Physical Backup: All physical files, including control files, data files, and archived redo logs, are copied as part of a physical backup.

- Logical Backup: Logical backups involve using tools like Oracle Data Pump or export utilities (exp, expdp) to backup schema objects such as tables, views, procedures, etc.

29) Explain the concept of Oracle ASM (Automatic Storage Management).

A file system and volume manager built into Oracle databases is called Oracle Automatic Storage Management (ASM). By automatically controlling the storage layout to improve I/O performance, it makes managing Oracle database files easier.  ASM helps efficiently handle large databases, ensure data redundancy, and balance data across available storage.

30) What are the main features of the Oracle Data Pump utility?

A powerful tool for importing and exporting data and metadata between databases is Oracle Data Pump. Key features include:

Faster Data Movement: It provides parallel data transfer, making it faster than traditional export/import utilities.

Fine-Grained Object Selection: Users can choose specific objects or schemas to export/import.

Compression: Data Pump supports compression of data to reduce disk space usage.

Remapping: You can remap tablespaces, schemas, and data files during the import process.

Additional Interview Questions for Experienced Professionals

1. What does BLOB data type mean in Oracle?

2. How is a post-database commit different from a post-form commit?

3. What is a logical backup?

4. What is redo log file mirroring in Oracle?

5. What are recursive hints in Oracle?

6. State the limitations of the CHECK constraint.

7. How many memory layers does the Oracle share pool have?

8. What do the terms save point and hash cluster mean in the Oracle database?

9. What are the various modules in Oracle forms?

10. Enumerate the differences between pre-select and pre-query.

 

 

Conclusion

These were some of the Oracle interview questions and their answers to help you pass your interview. Whether you are a fresher or an experienced professional, these questions cover basic Oracle interview questions, advanced Oracle interview questions, and Oracle technical interview questions. Preparing with these can give you the confidence to succeed in your Oracle interview.

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