Incorrect results in Database Trigger.

Gurus,

I'm getting incorrect values when using a trigger. When I execute the query in the trigger, manually, I get the correct values.

Example:

SQL>   CREATE TABLE "CMKAT"."ART_TEST" (        "ARTKEYI" NUMBER, "ARTBEZC" VARH
AR2(30 CHAR),"ARTVF1C" VARCHAR2(30 CHAR));

Table created.

SQL> CREATE TABLE "CMKAT"."PRO_TEST" (  "PROKEYI" NUMBER, "PROBEZC" VARCHAR2(30
CHAR), "PROVF1C" VARCHAR2(30 CHAR)) ;

Table created.

SQL>   CREATE TABLE "CMKAT"."LOOKUP" (  "LOOKUP_ARTKEYI" NUMBER, "LOOKUP_PROKEYI
" NUMBER);

Table created.

SQL> Insert into ART_TEST (ARTKEYI,ARTBEZC,ARTVF1C) values (3001,'pants',null);

1 row created.

SQL> Insert into ART_TEST (ARTKEYI,ARTBEZC,ARTVF1C) values (3002,'socks',null);

1 row created.

SQL> Insert into PRO_TEST (PROKEYI,PROBEZC,PROVF1C) values (4001,'outfit',null);

1 row created.

SQL> Insert into LOOKUP(LOOKUP_ARTKEYI,LOOKUP_PROKEYI) values (3001,4001);

1 row created.

SQL> Insert into LOOKUP(LOOKUP_ARTKEYI,LOOKUP_PROKEYI) values (3002,4001);

1 row created.

SQL> commit;

Commit complete.

SQL> SELECT LISTAGG(ARTBEZC,',') WITHIN GROUP (
ORDER BY ARTKEYI) CON,
  PROBEZC GRP
FROM ART_TEST,
  PRO_TEST,
  LOOKUP
WHERE ART_TEST.ARTKEYI = LOOKUP.LOOKUP_ARTKEYI
AND PRO_TEST.PROKEYI   = LOOKUP.LOOKUP_PROKEYI
GROUP BY PROBEZC;

CON                    GRP
----------------        --------
pants,socks       outfit

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Trigger:

CREATE OR REPLACE TRIGGER Trigg_Test before
  INSERT OR
  UPDATE ON ART_TEST FOR EACH ROW 
  DECLARE 
  ARTICLE_NAME VARCHAR2(100);
  ELEMENT_NAME VARCHAR2(100);
  BEGIN
    SELECT LISTAGG(:NEW.ARTBEZC,',') WITHIN GROUP (
    ORDER BY :new.ARTKEYI) CON,
      PROBEZC GRP
    INTO article_name,
      element_name
    FROM
      PRO_TEST,
      LOOKUP
    WHERE :new.ARTKEYI = LOOKUP.LOOKUP_ARTKEYI
    AND PRO_TEST.PROKEYI   = LOOKUP.LOOKUP_PROKEYI
    GROUP BY PROBEZC;
    INSERT INTO TEST_TABLE_FOR_TRIGGER VALUES
      (ARTICLE_NAME,ELEMENT_NAME);
  END;

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Test Trigger (Results):

SQL> UPDATE ART_TEST SET ARTVF1C = 'TEST'
where artkeyi in (3001,3002);

2 rows updated.

SQL> commit;

Commit complete.

SQL> SELECT * FROM TEST_TABLE_FOR_TRIGGER;

ART_CONCAT     ELEMENT
-------                     -------  
pants                   outfit
socks		     outfit

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Results should be:

ART_CONCAT     ELEMENT
-------                     -------  
pants,socks        outfit

Why am I getting different results when the trigger is executed and not the same results as the query?