🚀 Using Subqueries in Oracle SQL (Nested Queries Explained)

As part of my ongoing learning with Oracle Autonomous Database, I explored subqueries in SQL. Subqueries allow us to perform more complex queries by using the result of one query inside another.

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🎯 Objective

The goal of this activity was to:

• Understand how subqueries work

• Use nested queries to filter data

• Perform advanced SQL operations

💻 Step 1: Creating the Table

CREATE TABLE employees (
  emp_id NUMBER,
  emp_name VARCHAR2(50),
  salary NUMBER
);

🧪 Step 2: Inserting Data

INSERT INTO employees VALUES (1, 'Ali', 50000);
INSERT INTO employees VALUES (2, 'Ahmed', 70000);
INSERT INTO employees VALUES (3, 'Sara', 60000);
INSERT INTO employees VALUES (4, 'Zara', 65000);

📊 Step 3: Viewing Data

SELECT * FROM employees;

🔍 Step 4: Using Subquery

SELECT emp_name, salary
FROM employees
WHERE salary > (
    SELECT AVG(salary) FROM employees
);

This query returns employees whose salary is greater than the average salary.

💡 What I Learned

• How subqueries work in Oracle SQL

• Using nested queries for filtering

• Writing more advanced SQL logic

🚀 Conclusion

This activity helped me understand how subqueries can be used to perform complex data filtering. It is a powerful concept for real-world database applications.