Custom forms do not contain data blocks that are associated with specific database tables. Instead, they use SQL statements to manipulate data. These SQL statements are embedded in triggers (form triggers that are different from the database triggers) that run when a user performs an action such as clicking a button, e.g,. event. In a data block form, the triggers were generated automatically when you created the data block. In a custom form, the person who develops the form must write a trigger (an event procedure) for each button.