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Foreign Key

Foreign key ek database constraint hai jo ek table ke column ko doosri table ke primary key se link…

Overview

Foreign Key — Quick Facts

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Property: Detail

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Topic: Foreign Key

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Category: Database / Relational Database

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Full Name: Foreign Key Constraint

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Infobox

📚 | Property | Detail | |---|---| | Topic | Foreign Key | | Category | Database /…

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1. Parichay (Introduction)

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Customers table → customer…

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Orders table → order information

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Products table → product…

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Ek table ke column ko doosri table…

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2. Foreign Key Samajhna

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Parent Table (Referenced Table) —…

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Child Table (Referencing Table) —…

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Referential Integrity — guarantee…

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3. Kaise Kaam Karta Hai

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INSERT INTO Orders (customer_id,…

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UPDATE Orders SET customer_id =…

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FK constraint database engine…

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Application bugs se bhi data…

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4. Example: Orders aur Customers

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Order 101 ka customer_id = 1…

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Naya order customer_id = 2 (Priya)…

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Naya order customer_id = 99 →…

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Customer ID 1 (Rahul) delete karna…

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5. Referential Actions

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ON DELETE CASCADE → Customer…

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ON DELETE RESTRICT → Customer…

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ON DELETE SET NULL → Customer…

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6. Relationship Types

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1 Customer → Many Orders

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FK customer_id Orders table me

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Har order ka ek customer, ek…

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Students aur Courses → ek student…

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7. ER Diagram

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CUSTOMERS → ORDERS: One-to-Many (1…

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ORDERS → ORDER_ITEMS: One-to-Many…

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PRODUCTS → ORDER_ITEMS:…

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ORDER_ITEMS = junction-like table…

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8. Fayde aur Limitations

📚 Fayde: | # | Benefit | Description | |---|---|---| | 1 | Data Integrity | Invalid…

Diagram

Visual Flow

📊 Diagram visualization — details in narration

Quiz — Question 1

Foreign Key ka sabse sahi definition kya hai?

Quick Quiz

Quiz — Question 2

Foreign Key ka 'Topic' kya hai?

Complete! 🎉

Foreign Key Complete!

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Foreign Key Complete

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