Oracle Developer interview questions typically cover PL/SQL programming, database concepts, Oracle tools, and performance tuning. Here are 25 commonly asked Oracle Developer interview questions with answers to help you prepare effectively.
Q1. What is PL/SQL?
PL/SQL (Procedural Language/SQL) is Oracle’s procedural extension for SQL, allowing procedural constructs like loops, conditions, and exception handling within SQL statements.
Q2. What are the main components of PL/SQL?
PL/SQL blocks include the Declaration section, Execution section, and Exception Handling section.
Q3. What is a cursor in PL/SQL?
A cursor is a pointer that allows row-by-row processing of query results in PL/SQL.
Q4. What is the difference between implicit and explicit cursors?
Implicit cursors are automatically created by Oracle for single-row queries, while explicit cursors are defined by the programmer to handle multi-row queries.
Q5. What are triggers in Oracle?
Triggers are PL/SQL blocks that automatically execute in response to certain events on a table or view, such as INSERT, UPDATE, or DELETE.
Q6. What is the difference between a procedure and a function in PL/SQL?
Procedures perform actions and may not return a value, while functions must return a single value and can be used in SQL expressions.
Q7. What are packages in Oracle?
Packages are groups of related procedures, functions, variables, and other PL/SQL types stored together as a unit.
Q8. What is exception handling in PL/SQL?
Exception handling manages runtime errors using predefined or user-defined exceptions to prevent program termination.
Q9. How do you declare a variable in PL/SQL?
Using the syntax: variable_name datatype [NOT NULL] [:= initial_value]; in the declaration section.
Q10. What is a record in PL/SQL?
A record is a composite data type that groups related data items of different types into a single unit.
Q11. What is a collection in PL/SQL?
Collections are data structures like arrays, tables, or lists to hold multiple values, including associative arrays, nested tables, and VARRAYs.
Q12. What is the difference between a nested table and a VARRAY?
Nested tables are unbounded and can be sparse; VARRAYs have a fixed size and preserve the order of elements.
Q13. How do you improve performance in PL/SQL?
By using bulk processing (FORALL and BULK COLLECT), minimizing context switches, proper indexing, and avoiding unnecessary computations.
Q14. What is dynamic SQL?
Dynamic SQL allows you to construct and execute SQL statements at runtime using the EXECUTE IMMEDIATE statement.
Q15. What is a materialized view?
A materialized view stores the results of a query physically and can be refreshed periodically to improve performance.
Q16. What is the difference between DELETE and TRUNCATE in Oracle?
DELETE removes rows one at a time and can be rolled back; TRUNCATE quickly removes all rows and cannot be rolled back.
Q17. What is a synonym in Oracle?
A synonym is an alias for another database object, like a table or view, simplifying access.
Q18. What is a sequence?
A sequence is a database object that generates unique numeric values, often used for primary key generation.
Q19. How do you handle exceptions in PL/SQL?
Using the EXCEPTION block with predefined exceptions like NO_DATA_FOUND and user-defined exceptions.
Q20. What is the difference between %ROWTYPE and %TYPE?
%ROWTYPE declares a record variable that represents an entire row of a table, while %TYPE declares a variable with the datatype of a specific column.
Q21. What is the difference between CHAR and VARCHAR2?
CHAR is fixed-length and pads spaces; VARCHAR2 is variable-length and only uses the required space.
Q22. What is the use of the ROWNUM pseudocolumn?
ROWNUM assigns a unique number to each row returned by a query before ordering, often used for limiting query results.
Q23. What is the difference between an INNER JOIN and an OUTER JOIN?
INNER JOIN returns matching rows from both tables; OUTER JOIN returns matching rows plus non-matching rows from one or both tables.
Q24. What is the use of the NVL function?
NVL replaces NULL values with a specified value.
Q25. How do you debug PL/SQL code?
Using DBMS_OUTPUT.PUT_LINE to print debug messages, PL/SQL debuggers in IDEs, and exception handling to catch errors.