PL/SQL 触发器在插入语句之前检查值

Question

I am new to PL/SQL and I have an issue regarding a trigger I am trying to implement.

The triggers purpose is to check a monetary value before it's inserted into the table to see if someone made a mistake during inserting. If they have, they will be given a message stating the value is incorrect. The values are in the billions so for now I am just checking if the value entered is above 10000 or not.

The trigger I currently have is;

CREATE TRIGGER Check_Value
BEFORE INSERT OR UPDATE OF "Potential Annual Value By 2026" ON AIPOTENTIALVALUEFORHEALTHCARE
BEGIN
IF (NEW."Potential Annual Value By 2026" < 10000.00) THEN
DBMS_OUTPUT.put_line('Value typed was incorrect');
ELSIF (NEW."Potential Annual Value By 2026" >= 10000.00) THEN
INSERT INTO AIPOTENTIALVALUEFORHEALTHCARE VALUES(NEW.ValueID, NEW.ApplicationID, NEW."Application Name", NEW.KeyDriverForAdoptionID, NEW."KeyDriverDescription", NEW."Potential Annual Value By 2026");
END IF;
END;

This will not work due to an error:

PLS-00201: identifier NEW.'Potential Annual Value By 2026' must be declared

My guess is that I have set the trigger incorrectly and that it doesn't know which value to check when it runs the trigger. From some research, I tried to use.NEW to pass the values of the statement into the trigger however I am not sure if this is the correct implementation.

I had tried the method already posted;

CREATE TRIGGER Check_Value
BEFORE INSERT OR UPDATE OF "Potential Annual Value By 2026" ON AIPOTENTIALVALUEFORHEALTHCARE
BEGIN
  IF (:NEW."Potential Annual Value By 2026" < 10000.00) THEN
    DBMS_OUTPUT.put_line('Value typed was incorrect');
  ELSIF (:NEW."Potential Annual Value By 2026" >= 10000.00) THEN
    INSERT INTO AIPOTENTIALVALUEFORHEALTHCARE VALUES
      (:NEW.ValueID, :NEW.ApplicationID, :NEW."Application Name", 
       :NEW.KeyDriverForAdoptionID, :NEW."KeyDriverDescription", 
       :NEW."Potential Annual Value By 2026");
  END IF;
END;

and recieved a different error:

ORA-04082: NEW or OLD references not allowed in table level triggers
04082. 00000 -  "NEW or OLD references not allowed in table level triggers"
*Cause:    The trigger is accessing "new" or "old" values in a table trigger.
*Action:   Remove any new or old references.

If this error is stating I can't use NEW references in a table level trigger, how would I be able to verify the contents of the insert statement before it is committed?

Answer 1

You are missing colons before the NEW keywords and the FOR EACH ROW clause. Also you do not need to (and must not) re-issue the INSERT within the trigger, it will happen anyway (if no error is raised):

CREATE TRIGGER Check_Value
BEFORE INSERT OR UPDATE OF "Potential Annual Value By 2026" ON AIPOTENTIALVALUEFORHEALTHCARE
FOR EACH ROW
BEGIN
  IF (:NEW."Potential Annual Value By 2026" < 10000.00) THEN
    RAISE_APPLICATION_ERROR(-20001, 'Value typed was incorrect');
  END IF;
END;

I'm sure this is just a training example, but DBMS_OUTPUT.PUT_LINE is not a suitable method for raising errors to users as its output can only be seen when using develpper tools like SQL Developer. Use RAISE_APPLICATION_ERROR . Also it doesn't actually raise an exception, so it won't prevent the insert at all.

In fact, this check might be better done with a CHECK constraint - assuming the column value must never be under 10000:

ALTER TABLE AIPOTENTIALVALUEFORHEALTHCARE
   ADD CONSTRAINT AIPOTENTIALVALUEFORHEALTHCARE_CHK_VALUE
      CHECK ("Potential Annual Value By 2026" >= 10000);