ALTER Command in SQL Explained in Detail | ADD, MODIFY, DROP, RENAME & Constraints with Examples

In this video, you will learn the ALTER Command in SQL with a complete practical and theoretical explanation. The ALTER command is a DDL (Data Definition Language) statement used to change the structure of an existing table without deleting the table itself. This video is perfect for students, beginners, interview preparation, exams, and database learners who want a clear understanding of how table structures can be modified after creation. 00:00 – Introduction to ALTER Command 00:37 – ADD (Add New Column) 01:59 – MODIFY TABLE 02:52 – RENAME COLUMN 03:33 – DROP COLUMN 04:23 – ADD & DROP CONSTRAINT 06:40 – RENAME TABLE 🔹 What You Will Learn in This Video ✔ What is the ALTER command in SQL ✔ Why ALTER is a DDL command ✔ Syntax and real-time examples ✔ Coding explanation with MySQL ✔ Important rules and characteristics 🔹 Topics Covered in Detail 🔸 1️⃣ ALTER TABLE ADD (Add New Column) Purpose of ADD Syntax explanation Practical example How existing rows behave NULL and DEFAULT behavior 🔸 2️⃣ ALTER TABLE MODIFY (Change Column Definition) Changing data type and size Increasing vs decreasing column size Risk of data loss How existing data is handled 🔸 3️⃣ ALTER TABLE RENAME COLUMN (MySQL 8+) Renaming columns safely Effect on data and constraints Syntax and example 🔸 4️⃣ ALTER TABLE DROP COLUMN Permanently removing a column Data deletion warning Why DROP cannot be rolled back 🔸 5️⃣ ALTER TABLE ADD CONSTRAINT Add PRIMARY KEY Add UNIQUE constraint Add FOREIGN KEY with parent–child relationship Add CHECK constraint Add DEFAULT value Syntax and use cases 🔸 6️⃣ ALTER TABLE DROP CONSTRAINT Drop PRIMARY KEY Drop UNIQUE constraint Drop FOREIGN KEY Important MySQL-specific syntax 🔸 7️⃣ ALTER TABLE RENAME TABLE Renaming an existing table Syntax and example When and why to use it 🔹 Important Characteristics of ALTER Command ✔ DDL Command (Auto-commit) ✔ Changes table structure, not records ✔ Cannot be rolled back ✔ Used after table creation 🎯 Who Should Watch This Video? SQL beginners Computer Science students Exam & interview aspirants MySQL learners Anyone preparing for DBMS, SQL, or backend development 📘 Notes & Examples are explained step-by-step for easy understanding. 👍 If you find this video helpful, LIKE, SHARE, and SUBSCRIBE to the channel for more SQL tutorials, DBMS concepts, and MCQ shorts. #ALTERCommand #SQLAlter #SQLTutorial #DDLCommands #SQLForBeginners #MySQL #DBMS #SQLConstraints #PrimaryKey #ForeignKey #UniqueConstraint #CheckConstraint #DefaultConstraint #RenameColumn #DropColumn #AddColumn #SQLWithExamples #SQLInterviewQuestions #ComputerScience #ProgrammingTutorial #DatabaseManagement #LearnSQL #SQLCoding