Oracle SQL Developer Interview Questions

Oracle SQL Developer Interview Questions and Answers

1. What is Oracle SQL Developer?

Answer:
Oracle SQL Developer is a free, integrated development environment (IDE) provided by Oracle for working with SQL, PL/SQL, databases, and reports. It helps in:

Writing and running SQL queries
Managing database objects
Debugging PL/SQL code
Importing/exporting data
Running reports and scripts

2. What are the features of Oracle SQL Developer?

Answer:
Key features include:

SQL worksheet for running queries
Database browser to view tables, views, indexes, etc.
PL/SQL editor with debugging tools
Data import/export from Excel, CSV, etc.
ER diagrams generation
Version control integration

3. What is the difference between SQL and PL/SQL?

SQL	PL/SQL
Structured Query Language	Procedural Language extension for SQL
Executes one statement at a time	Executes a block of code (procedure/function)
Mainly used for data manipulation	Used for business logic, loops, conditions
No error handling	Has built-in error handling (`EXCEPTION`)

4. How do you connect to a database in Oracle SQL Developer?

Answer:

Open SQL Developer.
Click the green + (New Connection) icon.
Enter:
- Connection Name
- Username & Password
- Hostname, Port (default: 1521)
- SID or Service Name
Click Test to check connection.
Click Connect to open the session.

5. What is a Primary Key?

Answer:
A Primary Key is a column or combination of columns that uniquely identifies each row in a table. It:

Cannot be NULL
Must be unique
Only one primary key allowed per table

📝 Example:

CREATE TABLE employees (
  emp_id NUMBER PRIMARY KEY,
  name VARCHAR2(100)
);

6. What is a Foreign Key?

Answer:
A Foreign Key is a column that creates a link between two tables. It refers to the primary key of another table to enforce referential integrity.

7. What is a JOIN? List types of joins.

Answer:
A JOIN is used to combine rows from two or more tables based on a related column.

Types of JOINS:

INNER JOIN – Matching rows only
LEFT JOIN – All rows from the left table, matching from right
RIGHT JOIN – All rows from the right table
FULL JOIN – All rows from both tables
CROSS JOIN – Cartesian product

8. What are Views in Oracle?

Answer:
A View is a virtual table based on the result of a query. It does not store data itself.

📝 Example:

CREATE VIEW emp_view AS 
SELECT emp_id, name 
FROM employees 
WHERE status = 'ACTIVE';

9. What is a Cursor?

Answer:
A Cursor is a pointer to the result set of a SQL query. It is used in PL/SQL to process rows one at a time.

Types:

Implicit Cursor – Automatically used by Oracle
Explicit Cursor – Declared and controlled by the programmer

10. What is a sequence in Oracle?

Answer:
A Sequence is used to generate unique numeric values, typically for primary keys.

📝 Example:

CREATE SEQUENCE emp_seq START WITH 1 INCREMENT BY 1;

Oracle SQL Developer Interview Questions