# Accessing before and after rows

Many trigger actions need to access the values of the rows being changed.

Such trigger actions need to know one or both of the following:

- The "before" values of the rows being changed (their values before the database event that caused the trigger to fire)
- The "after" values of the rows being changed (the values to which the database event is setting them)

Derby provides transition variables and transition tables for a trigger action to access these values. See "Referencing old and new values: the REFERENCING clause" under the "CREATE TRIGGER statement" topic in the Derby Reference Manual.

Parent topic: Programming trigger actions
Related concepts
Trigger action overview
Performing referential actions
Triggers and exceptions
Related reference
Examples of trigger actions