Top 101+ Oracle Interview Questions and Answers in 2026
Introduction
This guide brings together Oracle Interview Questions and Answers for freshers, experienced professionals, students, career changers, and candidates preparing for database-related roles. The questions move from basic concepts to SQL, PL/SQL, database objects, performance, transactions, and practical interview scenarios.
Oracle’s current documentation covers SQL and PL/SQL as core parts of Oracle AI Database, while newer 26ai capabilities also extend into areas such as Boolean and vector data types and AI-assisted database interaction.
If you are preparing in Chennai, combining interview practice with structured Oracle Training in Chennai can help you build both conceptual knowledge and hands-on confidence.
Table of Contents
- Basic Oracle Interview Questions
- SQL Interview Questions
- Advanced SQL Questions
- PL/SQL Interview Questions
- Oracle Database Questions
- Performance and Scenario-Based Questions
- How to Prepare for an Oracle Interview
- FAQs
- Conclusion
1. Basic Oracle Interview Questions and Answers
1. What is Oracle Database?
Oracle Database is a relational database management system used to store, manage, and retrieve structured data.
2. What is SQL?
SQL is the language used to query and manage relational database data.
3. What is PL/SQL?
PL/SQL is Oracle’s procedural extension of SQL for writing database programs.
4. What is a table?
A table stores related data in rows and columns.
5. What is a row?
A row represents one record in a table.
6. What is a column?
A column represents a specific attribute of stored data.
7. What is a primary key?
A primary key uniquely identifies each row in a table.
8. What is a foreign key?
A foreign key links a column to another table’s key.
9. What is a unique key?
A unique key prevents duplicate values in a column or column combination.
10. What is a constraint?
A constraint controls the type of data allowed in a table.
11. What is a view?
A view is a stored SQL query presented like a virtual table.
12. What is a sequence?
A sequence generates numeric values, commonly for identifiers.
13. What is a synonym?
A synonym provides an alternative name for a database object.
14. What is a schema?
A schema is a collection of database objects owned by a user.
15. What is normalization?
Normalization organizes data to reduce unnecessary duplication.
16. What is denormalization?
Denormalization intentionally adds redundancy to improve specific query performance.
17. What is NULL?
NULL represents missing, unknown, or unavailable data.
18. What is DDL?
DDL defines database structures using commands such as CREATE and ALTER.
19. What is DML?
DML changes data using commands such as INSERT, UPDATE, and DELETE.
20. What is DCL?
DCL manages database privileges using commands such as GRANT and REVOKE.
2. SQL Interview Questions and Answers
21. What does SELECT do?
SELECT retrieves data from one or more tables.
22. What does WHERE do?
WHERE filters rows according to specified conditions.
23. What does ORDER BY do?
ORDER BY sorts query results.
24. What does GROUP BY do?
GROUP BY creates groups for aggregate calculations.
25. What does HAVING do?
HAVING filters grouped results after aggregation.
26. What is DISTINCT?
DISTINCT removes duplicate result rows.
27. What is an alias?
An alias gives a temporary name to a column or table.
28. What is an aggregate function?
It calculates values across multiple rows, such as SUM or COUNT.
29. Name common aggregate functions.
COUNT, SUM, AVG, MIN, and MAX are common examples.
30. What is a JOIN?
A JOIN combines related data from multiple tables.
31. What is an INNER JOIN?
It returns rows having matching values in both tables.
32. What is a LEFT JOIN?
It returns all left-table rows and matching right-table rows.
33. What is a RIGHT JOIN?
It returns all right-table rows and matching left-table rows.
34. What is a FULL OUTER JOIN?
It returns matched and unmatched rows from both tables.
35. What is a SELF JOIN?
A table is joined with itself using aliases.
36. What is a CROSS JOIN?
It produces combinations of rows from both tables.
37. What is a subquery?
A subquery is a query nested inside another SQL statement.
38. What is a correlated subquery?
It depends on values from the outer query.
39. What is UNION?
UNION combines compatible query results and removes duplicates.
40. What is UNION ALL?
UNION ALL combines results while retaining duplicates.
41. What is INTERSECT?
It returns rows common to both query results.
42. What is MINUS?
It returns rows found in the first result but not the second.
43. What is a CASE expression?
CASE performs conditional logic inside SQL statements.
44. What is NVL?
NVL replaces a NULL value with a specified value.
45. What is COALESCE?
COALESCE returns the first non-NULL expression.
46. What is a scalar function?
It returns one result for each input row.
47. What is a date function?
It performs operations involving date and time values.
48. What is an index?
An index helps the database locate rows more efficiently.
49. Can indexes slow operations?
Yes. They can increase storage and affect INSERT, UPDATE, and DELETE performance.
50. What is a composite index?
It is an index created using multiple columns.
3. Advanced SQL Interview Questions
51. What is a window function?
It calculates values across related rows without collapsing them.
52. What is ROW_NUMBER()?
It assigns a unique sequential number to result rows.
53. What is RANK()?
It assigns rankings while allowing gaps after ties.
54. What is DENSE_RANK()?
It assigns rankings without gaps after tied values.
55. What is a CTE?
A Common Table Expression creates a temporary named query result.
56. What is MERGE?
MERGE can insert or update rows depending on matching conditions.
57. What is a materialized view?
It stores the result of a query physically for faster access.
58. DELETE vs TRUNCATE?
DELETE can remove selected rows; TRUNCATE removes all rows more directly.
59. What is a transaction?
A transaction is a logical unit of database work.
60. What is COMMIT?
COMMIT permanently saves transaction changes.
61. What is ROLLBACK?
ROLLBACK reverses uncommitted transaction changes.
62. What is SAVEPOINT?
SAVEPOINT creates a point to which a transaction can roll back.
63. What is referential integrity?
It ensures relationships between related tables remain valid.
64. What is a Cartesian product?
It occurs when every row from one table combines with every row of another.
65. How do you find duplicate records?
GROUP BY the relevant columns and use HAVING COUNT(*) > 1.
66. How do you find the second-highest salary?
Use ranking, a subquery, or an ordered result with appropriate filtering.
67. How do you find the highest salary by department?
Group or rank employees by department and salary.
68. What is an execution plan?
It describes how Oracle intends to execute a SQL statement.
69. Why is SQL tuning important?
It helps reduce unnecessary resource usage and improve query response time.
70. What is query optimization?
It is the process of finding a more efficient execution approach.
Oracle’s SQL documentation includes detailed guidance for SELECT, joins, grouping, and query behavior.
4. PL/SQL Interview Questions
71. What is a PL/SQL block?
It is the basic program unit containing declarations, executable statements, and optional exception handling.
72. What are PL/SQL sections?
Declaration, execution, and exception-handling sections.
73. What is a procedure?
A procedure is a stored PL/SQL program that performs an operation.
74. What is a function?
A function returns a value to its caller.
75. Procedure vs function?
A function must return a value; a procedure does not require one.
76. What is a cursor?
A cursor processes query results row by row.
77. What is an implicit cursor?
Oracle automatically creates it for certain SQL statements.
78. What is an explicit cursor?
The programmer defines and controls it.
79. What is a trigger?
A trigger automatically executes when specified database events occur.
80. What is a package?
A package groups related PL/SQL procedures, functions, variables, and other elements.
81. What are package specification and body?
The specification exposes declarations; the body contains implementation details.
82. What is an exception?
An exception represents an error or unusual condition during execution.
83. What is exception handling?
It provides controlled responses to runtime errors.
84. What is BULK COLLECT?
It retrieves multiple rows into collections in fewer operations.
85. What is FORALL?
FORALL performs bulk DML operations efficiently.
86. What is %TYPE?
It derives a variable’s datatype from an existing column or variable.
87. What is %ROWTYPE?
It creates a record matching an entire table or cursor row.
88. What is dynamic SQL?
It builds and executes SQL statements dynamically at runtime.
89. What is DBMS_OUTPUT?
It displays messages generated from PL/SQL programs.
90. What is autonomous transaction?
It is an independent transaction that can commit or roll back separately.
Oracle’s current PL/SQL reference covers blocks, variables, subprograms, packages, triggers, cursors, error handling, and other core programming concepts.
5. Oracle Database and Scenario-Based Questions
91. How would you improve a slow query?
Check the execution plan, joins, filters, indexes, statistics, and unnecessary data retrieval.
92. What would you check before creating an index?
Check query patterns, selectivity, existing indexes, DML frequency, and storage impact.
93. How do you prevent SQL injection?
Use bind variables, parameterized queries, validation, and controlled database privileges.
94. What is a bind variable?
It is a variable supplied separately from the SQL statement.
95. Why should SELECT * be avoided?
It may retrieve unnecessary columns and create avoidable processing or maintenance issues.
96. How do you identify duplicate data?
Use GROUP BY with HAVING COUNT(*) > 1.
97. How do you delete duplicates safely?
Identify duplicates with a ranking strategy, verify the target rows, then delete carefully.
98. What is a deadlock?
A deadlock occurs when transactions wait on resources held by each other.
99. What is database security?
It protects data through authentication, authorization, privileges, auditing, and secure development practices.
100. What should a fresher know for an Oracle interview?
Focus on SQL, joins, constraints, subqueries, functions, transactions, indexes, and basic PL/SQL.
101. What should an experienced Oracle candidate prepare?
Prepare advanced SQL, PL/SQL, performance tuning, execution plans, database design, troubleshooting, and project scenarios.
102. What is new to explore in Oracle 26ai?
Oracle AI Database 26ai introduces capabilities including SQL BOOLEAN support, vector-related functionality, and AI-oriented database features.
Practical Oracle Interview Preparation Roadmap
Do not try to memorize all 101+ answers in one sitting. Instead, prepare in stages.
[Stage ]1 – Fundamentals: Learn tables, keys, constraints, data types, normalization, SQL commands, and transactions.
2 – SQL: Practice SELECT, WHERE, JOIN, GROUP BY, HAVING, subqueries, aggregate functions, set operators, and window functions.
3 – PL/SQL: Learn blocks, procedures, functions, cursors, triggers, packages, exceptions, and bulk processing.
4 – Real-time practice: Solve employee salary, department, duplicate-record, ranking, date, and transaction-based problems.
5 – Interview simulation: Explain your SQL logic aloud and practice writing queries without depending on autocomplete.
If you are starting from zero, a structured oracle course in Chennai can provide a learning sequence instead of studying disconnected interview questions.
Mid-Article Learning Tip
Don’t memorize SQL answers—understand why the query works. Interviewers often change the table structure or add a new condition. If you understand joins, filtering, grouping, subqueries, and ranking, you can adapt your answer to the new problem.
Common Mistakes Candidates Make
- Memorizing definitions without practicing SQL.
- Confusing WHERE and HAVING.
- Not understanding different JOIN types.
- Ignoring NULL handling.
- Writing inefficient queries without checking execution plans.
- Learning PL/SQL without understanding SQL fundamentals.
- Giving theoretical answers without explaining a real project example.
- Forgetting transaction concepts such as COMMIT and ROLLBACK.
Frequently Asked Questions [Oracle Interview Questions and Answers]
1. Are Oracle Interview Questions and Answers useful for freshers?
Yes. They provide a structured way to revise SQL, database concepts, and PL/SQL before an interview. Freshers should combine question-based revision with hands-on query practice because interviewers may ask candidates to write or explain SQL rather than simply define concepts.
2. Which Oracle topics should beginners learn first?
Start with SQL fundamentals, SELECT statements, filtering, joins, aggregate functions, GROUP BY, subqueries, constraints, indexes, transactions, and basic PL/SQL. Once these concepts are comfortable, move toward performance tuning and scenario-based questions.
3. Is Oracle suitable for non-technical graduates?
Yes, beginners from different academic backgrounds can learn database concepts progressively. A practical learning path should start with basic SQL, use simple datasets, and gradually introduce PL/SQL, database administration concepts, and real-world exercises.
4. What SQL questions are commonly asked in Oracle interviews?
Common areas include joins, subqueries, GROUP BY, HAVING, aggregate functions, duplicate records, ranking, NULL handling, indexes, transactions, and query optimization. Candidates with experience may also face scenario-based performance and troubleshooting questions.
5. How can I prepare for an Oracle interview in Chennai?
Build SQL fundamentals, practice Oracle-specific syntax, create small database projects, solve interview queries, and participate in mock interviews. If you prefer guided learning, compare an Oracle Training in Chennai program based on syllabus, practical sessions, trainer experience, projects, and interview preparation.
Conclusion
Preparing for an Oracle interview is easier when you study concepts in the right order instead of trying to memorize hundreds of isolated answers. Use these Oracle Interview Questions and Answers as a revision checklist, then practice each topic with real SQL problems.
If you are planning a database career, structured Oracle Training in Chennai can help you move from SQL fundamentals to practical Oracle and PL/SQL skills. Choose a program that emphasizes hands-on exercises, projects, troubleshooting, and interview preparation rather than theory alone.
Final CTA
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