Triggers, trigger events, and triggered actions

A trigger is an object that initiates an action when an UPDATE, DELETE, or INSERT operation is run against a table. The action is called a triggered action and the operation is called a trigger event.

Triggered actions can perform such tasks as:

• Synchronizing other tables with changes made by trigger events.

• Validating input data.

• Generating values for newly-inserted rows.

• Invoking functions to perform such tasks as issuing alerts.

• Enforcing business rules (for example, salary cannot be increased by more than 10 percent). A trigger can enforce a business rule globally; this saves users from coding the rule in every application that applies it.

For example, suppose that each row in table EMPLOYEE contains information about an employee of a company, and that a column in table COMPANY_STATS contains a value denoting the number of employees in the company. You can specify a triggered action that increases this value by 1 whenever a row of information about a new employee is inserted into EMPLOYEE.

The following links provide additional information on triggers:

• When triggered actions occur

• SQL for triggered actions:

  • SQL for triggered actions: summary

  • Transition variables and correlation names

  • Temporary tables

[ Top of Page | Table of Contents | Glossary | Index ]

[ DB2 List of Books | Search the DB2 Books ]