6.4. Trigger Body
The trigger body is written in PL/SQL. There are PL/SQL expressions that only have meaning within a trigger body. These topics are covered in the following paragraphs.
A trigger body can refer to two states of a column value. The syntax for each state is:
:NEW.COLUMN_NAME :OLD.COLUMN_NAME
:NEW.COLUMN_NAME is the syntax for referencing a column value within the body of the row INSERT and UPDATE triggers. This expression evaluates to NULL in DELETE row triggers. It evaluates to the value included in the SQL INSERT or UPDATE statement.
If the SQL statement does not reference a column, the following rules apply:
For INSERT statements, :NEW.COLUMN_NAME is either NULL or the value of the DEFAULT used in creating the table.
For UPDATE ...
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