ALTER TABLE PLANT_RESOURCE_USE
ADD CONSTRAINT PLANT_RESOURCE_USE_FK FOREIGN KEY (PA_ID, RESOURCE_ID)
REFERENCES LK_PLANT_RESOURCES (PA_ID, RESOURCE_ID) ON UPDATE CASCADE ON DELETE CASCADE;

DELETE FROM PLANT_RESOURCE_USE
WHERE AMOUNT IS NULL;

UPDATE RDB$RELATION_FIELDS
SET RDB$NULL_FLAG=1
WHERE RDB$FIELD_NAME='AMOUNT' and RDB$RELATION_NAME='PLANT_RESOURCE_USE';

UPDATE PLANT_RESOURCE_USE
SET TIME_TAKEN=0
WHERE TIME_TAKEN IS NULL;

UPDATE RDB$RELATION_FIELDS
SET RDB$NULL_FLAG=1
WHERE RDB$FIELD_NAME='TIME_TAKEN' and RDB$RELATION_NAME='PLANT_RESOURCE_USE';