How to access Before and After Rows ?

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How to access 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.

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