Tell about your experience of modifying database structures using DDL commands.

In my practice, I have used DDL (Data Definition Language) commands to modify the database structure, such as:

• CREATE TABLE — creating new tables.
• ALTER TABLE — modifying the structure of existing tables (adding/removing columns, changing data types).
• DROP TABLE — deleting tables.

For example, to add a new column to the users table:

ALTER TABLE users ADD COLUMN last_login TIMESTAMP;

Or to change the data type of a column:

ALTER TABLE orders ALTER COLUMN amount TYPE DECIMAL(10,2);

In projects, I also used migrations (for example, with Liquibase or Flyway) to manage database schema changes consistently and in a team, which allows rolling back changes and tracking modification history.