trigger questions

`Zone.js` is a library used by Angular to manage and detect asynchronous operations, such as HTTP requests, setTimeout, and other asynchronous tasks. It extends JavaScript's execution context, known as 'zones,' to track asynchronous activities and ensure that Angular's change detection is triggered appropriately when such operations complete. By using `Zone.js`, Angular can automatically detect changes in the application state and update the view accordingly without requiring manual intervention. This seamless integration helps maintain a consistent and responsive user interface by handling asynchronous events and their impact on the application's data model.

To create a trigger in PostgreSQL, first define a function that performs the desired action. Then, use the `CREATE TRIGGER` statement to bind this function to a table event. For example: `CREATE FUNCTION log_update() RETURNS TRIGGER AS $$ BEGIN INSERT INTO log_table (table_name, changed_at) VALUES ('employees', CURRENT_TIMESTAMP); RETURN NEW; END; $$ LANGUAGE plpgsql;` and `CREATE TRIGGER trg_log_update AFTER UPDATE ON employees FOR EACH ROW EXECUTE FUNCTION log_update();`.