ORA-22903: MULTISET expression not allowed - oracle

Question

I have a table which have a field as nested table. I have a trigger on the first table, but it does not work and results on a :ORA-22903: MULTISET expression not allowed
CREATE OR REPLACE TYPE DIA_T as object
(dia varchar2(9),
hora varchar2(6));
CREATE OR REPLACE TYPE DIA_TAB IS TABLE OF DIA_T;
CREATE TABLE T_TALLER(
PK NUMBER GENERATED BY DEFAULT ON NULL AS IDENTITY,
...
DIAS DIA_TAB,
FEC_INI DATE NOT NULL,
FEC_FIN DATE NOT NULL,
...
CONSTRAINT CST_PRIMKEY_TALLER PRIMARY KEY (PK),
...
) NESTED TABLE DIAS STORE AS DIAS_TAB;
My trigger is:
CREATE OR REPLACE TRIGGER TRG_TALLER_AU_FEC_FIN AFTER UPDATE OF FEC_FIN ON T_TALLER FOR EACH ROW
BEGIN
FOR REC IN (SELECT T.DIA , T.HORA
FROM TABLE(:NEW.DIAS) T) LOOP
dbms_output.put_line(REC.DIA||' '||REC.HORA);
END LOOP;
END;
When I try something like that:
update t_taller set fec_fin = fec_fin + 20 where pk = 10;
I get the following error:
ORA-22903: MULTISET expression not allowed
ORA-06512: at "ESTAMPAS.TRG_TALLER_AU_FEC_FIN", line 3
ORA-04088: error during execution of trigger 'ESTAMPAS.TRG_TALLER_AU_FEC_FIN'
Can you help me to solve this problem?
Thanks in advance.
Regards,
UPDATE
The trigger I posted is a dummy, but the error i get for the real one is the same, my real trigger is this
CREATE OR REPLACE TRIGGER TRG_TALLER_AU_FEC_FIN AFTER UPDATE OF FEC_FIN ON T_TALLER FOR EACH ROW
BEGIN
IF :NEW.FEC_FIN >= :OLD.FEC_FIN THEN
Pkg_Utilidades.p_ins_taller_clase_grupo(:NEW.PK,(:OLD.FEC_FIN) + 1,:NEW.FEC_FIN,:NEW.DIAS,:NEW.AU_USU_INS);
ELSE
DELETE T_TALLER_CLASE
WHERE FK_TALLER = :NEW.PK
AND FEC_CLASE BETWEEN :NEW.FEC_FIN + 1 AND :OLD.FEC_FIN;
END IF;
END;
Something else to say, I have a "AFTER INSERT" Trigger, and it Works fine:
CREATE OR REPLACE TRIGGER TRG_TALLER_AI_CLASE AFTER INSERT ON T_TALLER FOR EACH ROW
BEGIN
DELETE T_TALLER_CLASE WHERE FK_TALLER = :NEW.PK;
Pkg_Utilidades.p_ins_taller_clase_grupo(:NEW.PK,:NEW.FEC_INI,:NEW.FEC_FIN,:NEW.DIAS,:NEW.AU_USU_INS);
END;
The procedure is:
PROCEDURE p_ins_taller_clase_grupo (p_taller NUMBER,
p_fec_ini DATE,
p_fec_fin DATE,
p_dias DIA_TAB,
p_user VARCHAR2) IS
p_output VARCHAR2(100);
v_dia NUMBER;
BEGIN
FOR REC IN (SELECT p_fec_ini + LEVEL - 1 FECHA,
DECODE(TO_CHAR(p_fec_ini + LEVEL - 1 , 'DAY'),'MONDAY ',1,'TUESDAY ',2,'WEDNESDAY',3,'THURSDAY ',4,'FRIDAY ',5,'SATURDAY ',6,7) DIA
FROM DUAL
CONNECT BY LEVEL <= p_fec_fin - p_fec_ini + 1) LOOP
BEGIN
SELECT D INTO v_dia
FROM (
SELECT decode(upper(T.dia),'LUNES',1,'MARTES',2,'MIERCOLES',3,'MIÉRCOLES',3,'JUEVES',4,'VIERNES',5,'SABADO',6,'SÁBADO',6,7) D
FROM TABLE(p_dias) T
)
WHERE D = REC.DIA;
P_INS_TALLER_CLASE (p_taller,REC.FECHA,Pkg_conf.CST_HORA,p_user,p_output);
EXCEPTION
WHEN NO_DATA_FOUND THEN
NULL;
END;
END LOOP;
END p_ins_taller_clase_grupo;
The insert Works fine:
SQL> insert into t_taller (FK_profesor,fk_danza,fk_local,fk_periodicidad,fec_ini,fec_fin,dias,AU_USU_INS) values (1,1,1,1,to_date('05/01/2019','dd/mm/yyyy'),to_date('27/01/2019','dd/mm/yyyy'),dia_tab(dia_t('SABADO','10:30'),dia_t('DOMINGO','10:30')),'EP_PL01');
1 row created.
SQL> commit;
Commit complete.
SQL> update t_taller set fec_fin = fec_fin + 20 where pk = 24;
update t_taller set fec_fin = fec_fin + 20 where pk = 24
*
ERROR at line 1:
ORA-22903: MULTISET expression not allowed
ORA-06512: at "ESTAMPAS.PKG_UTILIDADES", line 451
ORA-06512: at "ESTAMPAS.TRG_TALLER_AU_FEC_FIN", line 5
ORA-04088: error during execution of trigger 'ESTAMPAS.TRG_TALLER_AU_FEC_FIN'
The line 451 of the package, is inside the procedure, exactly here:
SELECT D INTO v_dia
FROM (
SELECT decode(upper(T.dia),'LUNES',1,'MARTES',2,'MIERCOLES',3,'MIÉRCOLES',3,'JUEVES',4,'VIERNES',5,'SABADO',6,'SÁBADO',6,7) D
FROM TABLE(p_dias) T
)
WHERE D = REC.DIA;
Sorry for not posted all the details from the begining, i wanted to summayrize and show just the error.
Regards

Answer 1

TABLE expression works if you are running a select query on the table itself.
Something like
SELECT T.DIA , T.HORA
FROM T_TALLER ,TABLE(:NEW.DIAS) T
But, you are not allowed to select from the Trigger owner as it leads to "table is mutating" error( ORA-04091 ).
You may instead loop through the nested table column using a simple for loop.
CREATE OR REPLACE TRIGGER trg_taller_au_fec_fin AFTER
UPDATE OF fec_fin ON t_taller
FOR EACH ROW
BEGIN
FOR i in 1 .. :new.dias.count
LOOP
dbms_output.put_line(:new.dias(i).dia || ' ' || :new.dias(i).hora);
END LOOP;
END;
/
By the way, as #XING mentioned, there's no use of dbms_output in a Trigger. You should rather consider logging them into a table.
Demo

Answer 2

As mentioned in my comments Triggers are used for handling of events on the table to . Although your posted script does not make much sense to me , however am giving the solution.
Also you simply cannot Select records from a Nested table. You need to use table operator to do so. Also in a trigger if you do Select on same table, you might land up is mutating, trigger/function. See below demo:
CREATE OR REPLACE TYPE dia_t AS OBJECT (
dia VARCHAR2(9),
hora VARCHAR2(6)
);
CREATE OR REPLACE TYPE DIA_TAB IS TABLE OF DIA_T;
CREATE TABLE t_taller (
pk NUMBER ,
dias dia_tab,
fec_ini DATE NOT NULL,
fec_fin DATE NOT NULL,
CONSTRAINT cst_primkey_taller PRIMARY KEY ( pk )
)
NESTED TABLE dias STORE AS dias_tab;
INSERT INTO t_taller VALUES (
1,
dia_tab(dia_t(
'A',
'B')
),
TO_DATE('10-Dec-2018','DD-Mon-YYYY'),
TO_DATE('10-Dec-2018','DD-Mon-YYYY')
);
CREATE OR REPLACE TRIGGER trg_taller_au_fec_fin
AFTER UPDATE OF fec_fin ON t_taller
FOR EACH ROW
BEGIN
FOR rec IN ( SELECT t.dia,
t.hora
FROM t_taller e,TABLE (e.dias ) t) --This is how you select records from nested table
LOOP
dbms_output.put_line(rec.dia || ' ' || rec.hora);
END LOOP;
END;
Output:
Error starting at line : 40 in command -
update t_taller set fec_fin = fec_fin + 20 where pk = 1
Error report -
ORA-04091: table SYSTM.T_TALLER is mutating, trigger/function may not see it
ORA-06512: at "SYSTM.TRG_TALLER_AU_FEC_FIN", line 2
ORA-04088: error during execution of trigger 'SYSTM.TRG_TALLER_AU_FEC_FIN'
So again you need to revisit your requirement.