DDL(Data Definition Language)

Ye SQL ka wo part hota hai jo database ke structure ko define ya modify karne ke kaam aata hai. Jaise table banana, columns add karna, table delete karna, etc.

Simple shabdon mein: DDL commands database ke structure ke design ko control karte hain.

 DDL ke Important Commands

 1. CREATE Command

Ye command naya table banane ke liye use hota hai.

 Syntax:

 Example:

 Diagram:

 2. ALTER Command

Ye command existing table ke structure ko modify karne ke liye hota hai.

 Examples:

• Naya column add karna:

• Column ka datatype change karna:

• Column delete karna:

 3. DROP Command

Ye command table ya database ko permanently delete kar deta hai.

 Example:

 Warning: Isse table ka data aur structure dono delete ho jata hai.

 4. TRUNCATE Command

Ye command table ka sara data delete kar deta hai, par table ka structure bacha ke rakhta hai.

 Example:

 DROP vs TRUNCATE:

• DROP: Structure aur data dono delete karta hai.

• TRUNCATE: Sirf data delete karta hai.

 5. RENAME Command

Ye command kisi table ya object ka naam badalne ke kaam aata hai.

 Example:

 Short Summary

 Real-Life Example

Sochiye ek Excel sheet hai:

• CREATE se new Excel sheet banti hai.

• ALTER se naye columns add ya change hote hain.

• DROP se pura sheet delete ho jata hai.

• TRUNCATE se sirf data delete hota hai, par sheet ka format safe rehta hai.

• RENAME se sheet ka naam badal jata hai.

 Important Points

• -> DDL commands structure ke design ke liye use hote hain, data ke liye nahi.

• -> Inme se zyada commands undo (rollback) nahi kiya ja sakta.

• -> Mostly ye commands DBAs ya developers use karte hain jab database design hota hai.