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Skill Topic ยท Cinematic

๐Ÿ“˜ SQL UNIQUE - Duplicate Values Allowed Nahi!

UNIQUE constraint ensure karta hai ke column me saari values alag-alag hon โ€” koi duplicate nahi! ๐Ÿ”’

Overview
๐ŸŒŸ

๐Ÿ“˜ SQL UNIQUE - Duplicate Values Allowed Nahi! โ€” Quick Facts

๐Ÿ“Œ

Database: Multiple NULLs in UNIQUE?

๐ŸŽฏ

MySQL: โœ… Multiple NULLs allowed

โšก

SQL Server: โŒ Sirf 1 NULL (by default)

๐Ÿ”‘

PostgreSQL: โœ… Multiple NULLs allowed

Topic 1
โœจ

๐Ÿ“Œ UNIQUE Kya Hai?

๐Ÿ“š UNIQUE constraint guarantee karta hai ke ek column (ya columns ka group) me koi do rowsโ€ฆ
Topic 2
๐Ÿ’ก ๐Ÿ“Š ๐Ÿ”ฌ

๐Ÿ“Œ UNIQUE in CREATE TABLE

๐Ÿ’ก Column Level: `sql CREATE TABLE Customers ( CustomerID INT NOT NULL, FirstNameโ€ฆ
Topic 3
๐Ÿ”’

๐Ÿ“Œ Test Examples

๐ŸŽฏ `sql -- โœ… Works: INSERT INTO Customers VALUES (1, 'Anil', 'Nayak', 'anil@mail.com',โ€ฆ
Topic 4
โญ

๐Ÿ“Œ Composite UNIQUE (Multiple Columns)

โญ Ek se zyada columns ka combination unique hona chahiye: `sql CREATE TABLE Enrollments (โ€ฆ
Topic 5
๐Ÿ“ฅ ๐Ÿ“ฅ ๐Ÿง  ๐Ÿ”ฌ ๐Ÿ’ก ๐ŸŽฏ

๐Ÿ“Œ ALTER TABLE se UNIQUE Add

๐Ÿ”‘ `sql -- Single column UNIQUE: ALTER TABLE Customers ADD CONSTRAINT uq_email UNIQUEโ€ฆ
Topic 6
โœจ ๐Ÿ“Š ๐Ÿ”ฌ

๐Ÿ“Œ UNIQUE Drop Karna

โœจ `sql -- MySQL: ALTER TABLE Customers DROP INDEX uq_email; -- SQL Server: ALTER TABLEโ€ฆ
Topic 7
โœจ

๐Ÿ“Œ UNIQUE + NOT NULL vs PRIMARY KEY

๐ŸŒŸ `sql -- Approach 1: PRIMARY KEY CREATE TABLE Users ( UserID INT PRIMARY KEY -- NOT NULL +โ€ฆ
Topic 8
๐Ÿš€

๐Ÿ“Œ UNIQUE aur NULL ka Behavior

๐Ÿš€ | Database | Multiple NULLs in UNIQUE? | |----------|--------------------------| | MySQLโ€ฆ
Topic 9
๐Ÿ“ฅ ๐Ÿ“ฅ ๐Ÿง  ๐Ÿ”ฌ ๐Ÿ’ก ๐ŸŽฏ

๐Ÿ“Œ Real-World Use Cases

๐Ÿ“š `sql CREATE TABLE Users ( UserID INT PRIMARY KEY, Username VARCHAR(50) NOT NULL UNIQUE,โ€ฆ
Topic 10
๐Ÿ’ก ๐Ÿ“Š ๐Ÿ”ฌ

โœ… Summary

๐Ÿ’ก KEY POINTS: - UNIQUE duplicate values band karta hai ek column me - Ek table me multipleโ€ฆ
Quick Quiz
๐Ÿง  QUIZ TIME

Quiz โ€” Question 1

๐Ÿ“˜ SQL UNIQUE - Duplicate Values Allowed Nahi! ka sabse sahi definition kya hai?

Quick Quiz
๐Ÿง  QUIZ TIME

Quiz โ€” Question 2

๐Ÿ“˜ SQL UNIQUE - Duplicate Values Allowed Nahi! ka 'MySQL' kya hai?

Complete! ๐ŸŽ‰
COMPLETE

๐Ÿ“˜ SQL UNIQUE - Duplicate Values Allowed Nahi! Complete!

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