Trigger Assignment Help

A trigger is procedural code that initiates an action when event like INSERT, DELETE or UPDATE occurs on particular table or view or a database. It is used for maintaining the integrity of the information on the Database Depending upon, when a trigger is fired, it may be classified as :

• Statement-Level Trigger
• Row-Level Trigger
• Before Triggers
• After Triggers

Trigger Syntax:

{`
  CREATE

  [DEFINER = {user | CURRENT_USER}]

  TRIGGER trigger_name

  trigger_time trigger_event

  ON tbl_name FOR EACH ROW

  trigger_body

  trigger_time: {BEFORE | AFTER}

  trigger_event: {INSERT | UPDATE | DELETE}

  `}

Database trigger is a PL/SQL block that is executed on an event in the database. The event is related to a particular data manipulation of a table such as inserting, deleting or updating a row of a table. Triggers may be used for any of the following:

• To implement complex business rule, which cannot be implemented using integrity constraints.
• To audit the process. For example, to keep track of changes made to a table.
• To automatically perform an action when another concerned action takes place. For example, updating a table whenever there is an insertion or a row into another table.
• Triggers are similar to stored procedures, but stored procedures are called explicitly and triggers are called implicitly by Oracle when the concerned event occurs.