Question

we want to create a trigger which checks if a new measurement (=messung) point lies within the current glacier shape (=umriss).

are tables look like this:

glacier shape (=Umriss)

create table umriss
(
 umr_nr       number (4) not null,
 umr_datum    date,
 GLST_ID      number (4) not null,
 shape        mdsys.sdo_geometry,
 GLETSCHER_ID number (3) not null
)
;

alter table umriss
add constraint umriss_glst_pk
primary key (umr_nr, GLST_ID, GLETSCHER_ID)
;

ALTER TABLE umriss 
ADD CONSTRAINT umriss_gletscherstand_fk 
FOREIGN KEY (GLST_ID, GLETSCHER_ID) 
REFERENCES GLETSCHERSTAND(GLST_ID, GLETSCHER_ID);

new measurement (=Messung)

CREATE TABLE MESSUNG
(
 MESS_NR      number (4) not null,
 MESS_DAT     date,
 MESS_AKK     number (20) NOT NULL,
 MESS_SCHMELZ number (20) NOT  NULL,
 SHAPE        mdsys.sdo_geometry,
 MESS_BILD    blob,  
 KMPGN_NR     NUMBER (4) NOT NULL
);

ALTER TABLE MESSUNG
ADD CONSTRAINT messung_pk
PRIMARY KEY (MESS_NR);

ALTER TABLE MESSUNG
ADD CONSTRAINT messung_messkampagne_fk
FOREIGN KEY (KMPGN_NR)
REFERENCES MESSKAMPAGNE(KMPGN_NR);

Trigger

CREATE OR REPLACE 
TRIGGER MESSUNG_in_UMRISS_TRI
BEFORE INSERT OR UPDATE ON MESSUNG
FOR EACH ROW
DECLARE 
   num_check NUMBER;
BEGIN 
   SELECT COUNT (*) INTO num_check
     FROM UMRISS u
    WHERE mdsys.sdo_contains (u.shape, :NEW.point) = 'TRUE';

   IF num_check <> 1
   THEN 
      RAISE_APPLICATION_ERROR (=20500, 'Messung in keinem Umriss')
   END IF; 
END; 

How do we iplement the function so the trigger only checks within the most curretn glacier shape?
Thanks for your help!

Answer 1

This will return the one row fron UMRISS which matches the most recent date in the table.

SELECT COUNT (*) INTO num_check
FROM UMRISS u
WHERE mdsys.sdo_contains (u.shape, :NEW.point) = 'TRUE'
AND u.umr_datum = ( select max(d.;umr_datum) from UMRISS d );

This sort of query is the price for keeping historical data in teh same table as the current record.