🚀 Now, Let’s move to the next topic:

✅ SQL Views vs Materialized Views

🧠 1. What is a View?

A View is a virtual table created from a query.

👉 Stores only the SQL query

👉 Does NOT store actual data

👉 Always shows latest data from underlying tables

CREATE VIEW employee_view AS

SELECT * FROM employees;

🧠 2. What is a Materialized View?

A Materialized View stores the query result physically.

👉 Stores actual data

👉 Faster for reporting queries

👉 Needs refresh to get latest data

CREATE MATERIALIZED VIEW employee_summary AS

SELECT department,

AVG(salary) AS avg_salary

FROM employees

GROUP BY department;

⚡ 3. View vs Materialized View

Feature : View : Materialized View

Stores Data : ❌ No : ✅ Yes

Storage Space : Very Low : Higher

Query Speed : Slower : Faster

Real-Time Data : ✅ Yes : ❌ Needs Refresh

Best For : OLTP Systems : Reporting & Analytics

🔥 4. Example

View

SELECT * FROM employee_view;

Every execution runs the underlying query again.

Materialized View

SELECT * FROM employee_summary;

Reads precomputed data directly.

🔄 5. Refresh Materialized View

REFRESH MATERIALIZED VIEW employee_summary;

Updates stored results with latest data.

🎯 6. Real-World Usage

Views Used In:

✔ Banking Applications

✔ HR Systems

✔ Transaction Systems

Materialized Views Used In:

✔ BI Dashboards

✔ Data Warehouses

✔ Reporting Systems

🎯 7. Practice Tasks

1. Create a view for high-salary employees

2. Query data from a view

3. Create department salary summary view

4. Create materialized view for sales summary

5. Refresh materialized view

⚡ Mini Challenge 🔥

👉 Create a materialized view showing:

• department

• total employees

• average salary

Then query it to find the department with the highest average salary.

Most asked interview question:

👉 When would you choose a Materialized View over a View?

✅ Answer: "When query execution is expensive and data changes less frequently, Materialized Views improve performance significantly."

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