Can you explain what the term 'trigger' means in the context of databases and how it is used?

In databases, a trigger is a special object that automatically performs a specified set of actions (such as SQL queries or procedures) in response to certain events, such as inserting (INSERT), updating (UPDATE), or deleting (DELETE) data in a table.

Triggers are used for:

• Automatic validation or modification of data upon changes.
• Maintaining change logs.
• Ensuring data integrity.
• Implementing business logic at the database level.

An example of a simple SQL trigger that records the change date when a new record is inserted into the "orders" table:

CREATE TRIGGER trg_set_order_date
BEFORE INSERT ON orders
FOR EACH ROW
BEGIN
  SET NEW.order_date = NOW();
END;