Data Definition Language - DDL

Data Definition Language (DDL) is a part of SQL (Structured Query Language) that deals with defining and managing the structure of a database. DDL commands modify the metadata of a database, such as information about tables, schemas, indexes, and other database objects, rather than manipulating the actual data.

Key DDL Commands:

1. CREATE
Used to create new database objects like tables, schemas, views, or indexes.
Example:

CREATE TABLE Kunden (
    ID INT PRIMARY KEY,
    Name VARCHAR(50),
    Alter INT
);

2. ALTER
Used to modify the structure of existing objects, such as adding or removing columns.
Example:

ALTER TABLE Kunden ADD Email VARCHAR(100);

3. DROP
Permanently deletes a database object, such as a table.
Example:

DROP TABLE Kunden;

4. TRUNCATE
Removes all data from a table while keeping its structure intact. It is faster than DELETE as it does not generate transaction logs.
Example:

TRUNCATE TABLE Kunden;

Characteristics of DDL Commands:

• Changes made by DDL commands are automatically permanent (implicit commit).
• They affect the database structure, not the data itself.

DDL is essential for designing and managing a database and is typically used during the initial setup or when structural changes are required.