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📊 Orders Table
| ID | Customer ID | Product ID | Quantity | Date |
|---|---|---|---|---|
| 1 | 101 | 201 | 2 | 2024-01-15 |
| 2 | 102 | 202 | 1 | 2024-01-16 |
| 3 | 101 | 203 | 3 | 2024-01-17 |
👥 Customers Table
| ID | Name | City | Phone | |
|---|---|---|---|---|
| 101 | राम शर्मा | मुंबई | ram@email.com | 9876543210 |
| 102 | श्याम गुप्ता | दिल्ली | shyam@email.com | 9876543211 |
| 103 | गीता पटेल | पुणे | geeta@email.com | 9876543212 |
📦 Products Table
| ID | Name | Price (₹) | Category | Stock |
|---|---|---|---|---|
| 201 | लैपटॉप | 50,000 | Electronics | 25 |
| 202 | मोबाइल | 20,000 | Electronics | 50 |
| 203 | हेडफोन | 2,500 | Electronics | 100 |
🔍View Creation
📋 Order Report View
CREATE VIEW order_report AS
SELECT
o.id,
c.name as customer_name,
p.name as product_name,
o.quantity,
o.quantity * p.price as total_amount,
o.date
FROM orders o
JOIN customers c ON o.customer_id = c.id
JOIN products p ON o.product_id = p.id;
View का इस्तेमाल कैसे करें:
-- View बनाना
CREATE VIEW simple_report AS
SELECT customer_name, product_name, total_amount
FROM order_report
WHERE total_amount > 10000;
-- View को use करना (बिल्कुल table की तरह)
SELECT * FROM simple_report;
-- View को update करना
CREATE OR REPLACE VIEW simple_report AS
SELECT customer_name, product_name, total_amount, date
FROM order_report
WHERE total_amount > 15000;
-- View को delete करना
DROP VIEW simple_report;
Table vs View:
| विशेषता | Table | View |
|---|---|---|
| Data Storage | ✅ Physical storage | ❌ Virtual (No storage) |
| Space Usage | 💾 Disk space लेता है | 🪶 कोई space नहीं |
| Data Freshness | ⏰ Manual update | 🔄 हमेशा fresh |
| Complex Queries | 🔍 हर बार लिखना पड़ता है | ✨ एक बार define करके reuse |
| Performance | ⚡ Fast (direct access) | 🐌 Slower (query execution) |
Practical Examples:
🎯 Simple View (Updatable)
CREATE VIEW mumbai_customers AS
SELECT id, name, email
FROM customers
WHERE city = 'मुंबई';
-- यह view में data update कर सकते हैं
UPDATE mumbai_customers
SET email = 'newemail@example.com'
WHERE id = 101;
🔒 Complex View (Read-only)
CREATE VIEW monthly_sales AS
SELECT
DATE_FORMAT(date, '%Y-%m') as month,
COUNT(*) as total_orders,
SUM(quantity * price) as total_revenue
FROM orders o
JOIN products p ON o.product_id = p.id
GROUP BY DATE_FORMAT(date, '%Y-%m');
-- यह view read-only है (GROUP BY के कारण)
SELECT * FROM monthly_sales;
🎮 Interactive Demo
Click buttons to see how views work:
👆 Upar ke buttons par click karke dekhein ki Views kaise kaam karte hain!"