How to create a column in MySQL that is automatically set to row creation or update time

1. Column that is automatically set to current time when row is created:
   

   column TIMESTAMP DEFAULT CURRENT_TIMESTAMP
   

2. Column that is is automatically set to current time when row is updated:
   

   column TIMESTAMP DEFAULT 0 ON UPDATE CURRENT_TIMESTAMP
   

3. Column that is automatically set to current time when row is created or updated:
   

   column TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
   

Complete example:

CREATE TABLE table (
id                INTEGER(10) UNSIGNED AUTO_INCREMENT,
last_updated      TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
created           DATETIME DEFAULT NULL,
);