Name some common DDL commands.

Common Data Definition Language (DDL) commands include:

1. **CREATE**: Defines new database objects such as tables, indexes, or views.

   - Example: `CREATE TABLE employees (id INT PRIMARY KEY, name VARCHAR(100));`

2. **ALTER**: Modifies the structure of an existing database object.

   - Example: `ALTER TABLE employees ADD COLUMN email VARCHAR(255);`

3. **DROP**: Deletes a database object, such as a table, index, or view.

   - Example: `DROP TABLE employees;`

4. **TRUNCATE**: Removes all records from a table but retains the table structure for future use.

   - Example: `TRUNCATE TABLE employees;`

5. **RENAME**: Changes the name of an existing database object.

   - Example: `RENAME TABLE employees TO staff;`

These commands are essential for defining and managing the schema of a database.