Skill Topic · Cinematic

📘 SQL UNIQUE - Duplicate Values Allowed Nahi!

UNIQUE constraint ensure karta hai ke column me saari values alag-alag hon — koi duplicate nahi! 🔒

Overview

📘 SQL UNIQUE - Duplicate Values Allowed Nahi! — Quick Facts

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Database: Multiple NULLs in UNIQUE?

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MySQL: ✅ Multiple NULLs allowed

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SQL Server: ❌ Sirf 1 NULL (by default)

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PostgreSQL: ✅ Multiple NULLs allowed

Topic 1

📌 UNIQUE Kya Hai?

📚 UNIQUE constraint guarantee karta hai ke ek column (ya columns ka group) me koi do rows…

Topic 2

📌 UNIQUE in CREATE TABLE

💡 Column Level: `sql CREATE TABLE Customers ( CustomerID INT NOT NULL, FirstName…

Topic 3

📌 Test Examples

🎯 `sql -- ✅ Works: INSERT INTO Customers VALUES (1, 'Anil', 'Nayak', 'anil@mail.com',…

Topic 4

📌 Composite UNIQUE (Multiple Columns)

⭐ Ek se zyada columns ka combination unique hona chahiye: `sql CREATE TABLE Enrollments (…

Topic 5

📌 ALTER TABLE se UNIQUE Add

🔑 `sql -- Single column UNIQUE: ALTER TABLE Customers ADD CONSTRAINT uq_email UNIQUE…

Topic 6

📌 UNIQUE Drop Karna

✨ `sql -- MySQL: ALTER TABLE Customers DROP INDEX uq_email; -- SQL Server: ALTER TABLE…

Topic 7

📌 UNIQUE + NOT NULL vs PRIMARY KEY

🌟 `sql -- Approach 1: PRIMARY KEY CREATE TABLE Users ( UserID INT PRIMARY KEY -- NOT NULL +…

Topic 8

📌 UNIQUE aur NULL ka Behavior

🚀 | Database | Multiple NULLs in UNIQUE? | |----------|--------------------------| | MySQL…

Topic 9

📌 Real-World Use Cases

📚 `sql CREATE TABLE Users ( UserID INT PRIMARY KEY, Username VARCHAR(50) NOT NULL UNIQUE,…

Topic 10

✅ Summary

💡 KEY POINTS: - UNIQUE duplicate values band karta hai ek column me - Ek table me multiple…

Quick Quiz

Quiz — Question 1

📘 SQL UNIQUE - Duplicate Values Allowed Nahi! ka sabse sahi definition kya hai?

Quick Quiz

Quiz — Question 2

📘 SQL UNIQUE - Duplicate Values Allowed Nahi! ka 'MySQL' kya hai?

Complete! 🎉

📘 SQL UNIQUE - Duplicate Values Allowed Nahi! Complete!

Aliens School · HIEN · Cinematic Knowledge

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