3-2 1 CREATE, ALTER, DROP Explained

Key Concepts

• CREATE
• ALTER
• DROP

CREATE

The CREATE command is used to create new database objects such as tables, views, indexes, and schemas. It defines the structure and initial state of the object.

Example: Creating a new table named "Employees" with columns "EmployeeID," "Name," and "Department."

        CREATE TABLE Employees (
            EmployeeID INT PRIMARY KEY,
            Name VARCHAR(100),
            Department VARCHAR(50)
        );
    

ALTER

The ALTER command is used to modify the structure of existing database objects. It can add, delete, or modify columns and constraints in a table.

Example: Adding a new column "Email" to the "Employees" table.

        ALTER TABLE Employees
        ADD Email VARCHAR(100);
    

DROP

The DROP command is used to remove existing database objects such as tables, views, indexes, and schemas. It permanently deletes the object and its data.

Example: Dropping the "Employees" table.

        DROP TABLE Employees;
    

Examples and Analogies

CREATE: Think of CREATE as building a new house. You define the layout, rooms, and initial furnishings.

ALTER: Think of ALTER as renovating an existing house. You add new rooms, modify existing ones, or change the layout.

DROP: Think of DROP as demolishing a house. Once you drop an object, it is gone, and all its contents are lost.

Conclusion

Understanding the CREATE, ALTER, and DROP commands is essential for managing database objects effectively. These commands allow you to create new structures, modify existing ones, and remove unnecessary objects, ensuring your database remains organized and efficient.