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Overview

Copyright (c) A|iens. All rights reserved. — Quick Facts

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Property: Detail

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Full Name: Primary Key (PK)

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Type: Database Constraint / Column…

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Core Constraints: UNIQUE + NOT NULL

Topic 1

Infobox

📚 | Property | Detail | |---|---| | Full Name | Primary Key (PK) | | Type | Database…

Topic 2

1. Core Properties of Primary Key

💡 Primary key ke chaar fundamental properties hain: | Property | Description | Enforcement…

Topic 3

2. Primary Key vs Other Keys

🎯 Relational theory me multiple key types hain — har ek ka apna role hai: | Key Type |…

Topic 4

3. Natural Key vs Surrogate Key

⭐ Yeh database design ka sabse debated topic hai: | Aspect | Natural Key | Surrogate Key |…

Topic 5

4. Key Generation Strategies

🔑 Primary key value kahan se aayegi? Multiple strategies hain: | Strategy | Format | Size |…

Topic 6

5. Composite Primary Key

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Junction tables (many-to-many…

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Time-series data:…

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Multi-tenant data:…

Topic 7

6. Primary Key and Foreign Key Relationship

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ON DELETE CASCADE — parent row…

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ON DELETE SET NULL — parent delete…

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ON DELETE RESTRICT — parent delete…

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ON UPDATE CASCADE — parent PK…

Topic 8

7. Primary Key and Indexing

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Lookup by PK: O(log n) — very fast…

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Range scan: Efficient (leaves are…

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Insert: O(log n) for finding…

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Sequential PK inserts: Very…

Topic 9

8. Primary Key vs Unique Key

📚 | Aspect | Primary Key | Unique Key | |---|---|---| | Purpose | Main row identifier |…

Topic 10

9. Primary Key in Different Databases

💡 Har database ka apna PK behavior hai: | Feature | MySQL (InnoDB) | PostgreSQL | SQL…

Topic 11

10. Primary Key in ORMs

🎯 ORMs (Object-Relational Mappers) primary keys ko apne tareeqe se handle karte hain: |…

Topic 12

11. Primary Key Design Patterns

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Single server, simple app →…

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Distributed, need mergeability →…

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Privacy (hide record count) → UUID…

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Many-to-many junction → Composite…

Topic 13

12. Primary Key in Distributed Systems

🔑 Distributed systems me primary key generation unique challenges laata hai: Problem:…

Topic 14

13. Primary Key Anti-Patterns

✨ | Anti-Pattern | Description | Impact | Fix | |---|---|---|---| | No Primary Key | Table…

Topic 15

14. Common Mistakes

🌟 1. PK define nahi karna — "Baad me add kar lunga" mindset se problems aate hain. Table…

Topic 16

15. Best Practices

🚀 1. Hamesha PK define karo — Har table me explicit primary key honi chahiye. Exception…

Topic 17

16. Glossary

📚 | Term | Definition | |---|---| | Primary Key (PK) | Column ya columns jo table ki har…

Topic 18

19. Disclaimer

💡 Yeh article Aliens Wiki ka part hai aur educational/reference purposes ke liye likha gaya…

Comparison

2. Primary Key vs Other Keys

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Primary Key: Chosen unique identifier…

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Candidate Key: Any column/set that…

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Alternate Key: Candidate key that was…

Comparison

3. Natural Key vs Surrogate Key

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Definition: Business data se directly…

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Examples: Email, phone, ISBN, SSN, PAN

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Business Meaning: Yes — key itself…

Comparison

8. Primary Key vs Unique Key

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Purpose: Main row identifier

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NULL allowed: No (never)

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Per table: Exactly 1

Diagram

Visual Flow

📊 Diagram visualization — details in narration

Quiz — Question 1

Quick Quiz

Quiz — Question 2

Complete! 🎉

Aliens Wiki · HIEN · Cinematic Knowledge

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➡️

Copyright (c) A|iens. All rights reserved.

Copyright (c) A|iens. All rights reserved. — Quick Facts

Property: Detail

Full Name: Primary Key (PK)

Type: Database Constraint / Column…

Core Constraints: UNIQUE + NOT NULL

Infobox

1. Core Properties of Primary Key

2. Primary Key vs Other Keys

3. Natural Key vs Surrogate Key

4. Key Generation Strategies

5. Composite Primary Key

Junction tables (many-to-many…

Time-series data:…

Multi-tenant data:…

6. Primary Key and Foreign Key Relationship

ON DELETE CASCADE — parent row…

ON DELETE SET NULL — parent delete…

ON DELETE RESTRICT — parent delete…

ON UPDATE CASCADE — parent PK…

7. Primary Key and Indexing

Lookup by PK: O(log n) — very fast…

Range scan: Efficient (leaves are…

Insert: O(log n) for finding…

Sequential PK inserts: Very…

8. Primary Key vs Unique Key

9. Primary Key in Different Databases

10. Primary Key in ORMs

11. Primary Key Design Patterns

Single server, simple app →…

Distributed, need mergeability →…

Privacy (hide record count) → UUID…

Many-to-many junction → Composite…

12. Primary Key in Distributed Systems

13. Primary Key Anti-Patterns

14. Common Mistakes

15. Best Practices

16. Glossary

19. Disclaimer

2. Primary Key vs Other Keys

Primary Key: Chosen unique identifier…

Candidate Key: Any column/set that…

Alternate Key: Candidate key that was…

3. Natural Key vs Surrogate Key

Definition: Business data se directly…

Examples: Email, phone, ISBN, SSN, PAN

Business Meaning: Yes — key itself…

8. Primary Key vs Unique Key

Purpose: Main row identifier

NULL allowed: No (never)

Per table: Exactly 1

Visual Flow

See Also

Foreign_key

Index

SQL

Relational_database

Database_normalization

UUID

Quiz — Question 1

Quiz — Question 2

Copyright (c) A|iens. All rights reserved. Complete!

Copyright (c) A|iens. All rights reserved. Complete

Foreign_key