Top 20 Oracle SQL Interview Questions for Freshers and Experienced

Oracle SQL is one of the most common database systems employed in all industries for storage and analysis of information related to their operations. Companies need employees who have the skills of writing good queries and knowledge of database concepts to be able to solve any database problem.

Oracle SQL interview preparation includes not only a thorough knowledge of SQL basics but also of advanced SQL features such as indexing and query optimization. While freshers are usually assessed on their knowledge of SQL basics, the professionals are evaluated on the basis of database scenarios and optimization techniques.

This guide presents 20 Oracle SQL interview questions and answers for freshers as well as experienced professionals to aid your preparation. Candidates aspiring to gain solid knowledge of databases can opt for structured training programs available on various platforms including Oracle Course Online at Srijan Institute.

Top 20 Oracle SQL Interview Questions for Freshers and Experienced Candidates

Oracle SQL Interview Questions for Freshers

Q1. What is Oracle SQL and why is it used?

A. Oracle SQL is a structured query language which can be used to control Oracle databases in regard to the storage, manipulation, and retrieval of information from the databases. Oracle SQL helps programmers and database managers perform various database transactions. Businesses adopt Oracle SQL due to its good level of security, reliability, scalability, and capacity to process large amounts of data within an enterprise setting.

Q2. What are the main types of SQL commands in Oracle?

A. The Oracle SQL commands can be divided into four types, which are DDL, DML, DCL, and TCL. DDL refers to Data Definition Language that helps manage the database structure by using commands such as CREATE, ALTER, and DROP. DML is the Data Manipulation Language that manages the data through commands like INSERT, UPDATE, and DELETE.

Q3. What distinguishes a primary key from a foreign key?

A. The term “primary key” refers to a field in a database where each record has its own unique value. The primary key is designed to eliminate duplicates or NULL values. The “foreign key” is a concept employed to create relations between different tables using primary keys from other tables.

Q4. What are joins in Oracle SQL?

A. Joints are used whenever we need to connect two tables through the common columns. Five different kinds of joints are there which are offered by Oracle SQL, these include INNER JOINTS, LEFT JOINTS, RIGHT JOINTS, FULL OUTER JOINTS, and SELF JOINTS. It is very important for us to know about joints.

Q5. What is the difference between WHERE and HAVING clauses?

A. WHERE filters each record prior to any grouping taking place. HAVING filters records that have been grouped together using aggregate functions. WHERE can be used for all other conditions besides using the COUNT, SUM, and AVG functions with HAVING.

Q6. What are constraints in Oracle SQL?

A. Constraints refer to conditions imposed on the fields of a database so as to guarantee accuracy. Some of the commonly used constraints in Oracle SQL are: PRIMARY KEY, FOREIGN KEY, UNIQUE, NOT NULL, CHECK and DEFAULT.

Q7. What is the difference between DELETE, TRUNCATE, and DROP?

A. DELETE deletes the chosen record and also supports rollback prior to committing the record. TRUNCATE deletes all records quickly without supporting the rollback process. DROP deletes the entire table structure along with the data.

Q8. What are aggregate functions in Oracle SQL?

A. These aggregate functions work with multiple records to give a single result. Some of the aggregate functions used in Oracle SQL include COUNT, SUM, AVG, MAX, and MIN. Aggregate functions find extensive usage with GROUP BY.

Q9. What is normalization in Oracle databases?

A. Normalization is one of the methods used to design a database. This method involves arranging data in an efficient manner without duplication. Normalization also involves splitting of data into various tables in a logical way while ensuring a relationship between them.

Q10. What is a subquery in Oracle SQL?

A. Oracle SQL subqueries are queries embedded within another query to obtain temporary result sets. They can be applied with SELECT, INSERT, UPDATE, and DELETE commands. The main aim of subqueries is to make complex data extraction operations easier by breaking down large queries into simpler ones.

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Oracle SQL Interview Questions for Experienced Candidates

Q11. What is query optimization in Oracle SQL?

A. SQL query optimization increases performance by decreasing execution time and usage of resources. The Oracle optimizer formulates optimal execution plans taking into consideration available resources. Programmers optimize the performance of queries through indexing, optimization of poorly performing queries, execution plan analysis, and join optimization.

Q12. Explain indexes in Oracle SQL.

A. Indexes are special structures in a database that help in fastening data retrieval. There are various types of indexes supported by Oracle. Some examples include B-tree and bitmap indexes. Despite the fact that indexes enhance the performance of the SELECT statement, they might impact INSERT, UPDATE, and DELETE statements adversely.

Q13. What are Oracle SQL views?

A. Views are virtual tables created from the results of one or more SQL queries. They show the data contained in underlying tables but do not keep any records themselves. Views enhance security and make complex queries simpler.

Q14. What is the difference between RANK, DENSE_RANK, and ROW_NUMBER?

A. ROW_NUMBER, RANK, and DENSE_RANK are Oracle SQL analytic functions used to assign rankings to records based on specified conditions. ROW_NUMBER gives unique numeric rankings. The function RANK assigns the same rankings to duplicates and skips numbers after that. DENSE_RANK provides the same rankings but does not skip ranking numbers.

Q15. What are stored procedures in Oracle SQL?

A. Stored procedures are pre-compiled programs stored in the Oracle database system. The stored procedures have SQL commands and programming logic which can be executed whenever needed. Some of the advantages of using stored procedures are increased efficiency, improved security, less redundancy, and management of complex business processes.

Q16. What are Oracle SQL execution plans?

A. The Execution Plan reveals the manner in which Oracle processes the SQL statement by explaining the processes that are part of the execution, such as table scans, joins, and indexes. The developers utilize the execution plan to evaluate the efficiency of query execution. Execution Plans enable Database Administrators to improve the execution of SQL statements.

Q17. What are transactions in Oracle SQL?

A. Transactions refer to a collection of SQL statements which can be considered a single logical unit. The transactions in the Oracle database are ACID compliant. COMMIT will make changes permanent while ROLLBACK will undo changes made. SAVEPOINT creates recovery points.

Q18. What are triggers in Oracle SQL?

A. Triggers are those programs that run automatically upon the occurrence of some events in the database such as INSERT, UPDATE, or DELETE operations. Triggers are generally used for auditing purposes and implementing business logic into the database. But too many triggers may complicate the database.

Q19. How can you improve SQL query performance in Oracle?

A. Optimization of SQL can be achieved by means of proper indexing, optimization of joins, removing unnecessary columns, analysis of execution plans, and updating of statistics. Programmers need to be concerned with query optimization, as well as bottleneck identification to properly handle the large-scale application.

Q20. Explain the difference between Oracle SQL and PL/SQL?

A. Oracle SQL is a query language that can be used for querying data from Oracle databases, insertion of data into Oracle databases, updating data in Oracle databases, and management of data in Oracle databases. Oracle PL/SQL is an extension of SQL with capabilities for programming, like looping, conditional statements, variables, and exceptions.

Conclusion

Interview Preparation for Oracle SQL database needs a blend of theoretical and practical aspects. Beginners need to concentrate more on the basics of SQL queries, databases, and so on, whereas experienced persons need to improve their knowledge about optimization, indexing, execution plans, and so forth.

It is only through regular practice using realistic scenarios that candidates are able to gain more confidence and perform well in the technical interviews. Training offered by organizations such as Srijan Institute may help candidates to develop necessary skills for practical Oracle SQL. Explore more professional training programs and build strong SQL skills to enhance your career in DBMS.

FAQs Related to Oracle SQL Interview Questions

Q1. What are the most commonly asked Oracle SQL interview questions?

A. Most asked Oracle SQL Interview Questions and answers are given below which will help you in making your strong hold in Oracle SQL. Interviewers will also test whether candidates are able to write queries and problem-solve.

Q2. Which Oracle SQL topics should freshers prepare for interviews?

A. Oracle SQL topics that freshers need to learn for an interview are basics of Oracle SQL, database, SQL statements, joins, constraints, normalization, aggregate functions, queries and construction of queries.

Q3. Are Oracle SQL scenario-based questions asked in interviews?

A. Yes, Oracle SQL scenario based questions are quite common, particularly for hands-on positions. These interview questions test the candidates skills in terms of writing queries and performing tasks effectively.

Q4. What is the difference between Oracle SQL and PL/SQL in interviews?

A. Oracle SQL is a language designed for managing and querying data, while PL/SQL is a procedural language that extends SQL and includes features like loops, conditions, exceptions, etc.

Q5. How can I prepare for an Oracle SQL interview in 2026?

A. The candidate needs to do the exercises, try out advanced topics, solve real life scenarios and also learn on performance tuning. Oracle training programs would also help with preparation.