Using the SQL*Plus of Oracle 8i Personal Edition:

CREATE TABLE COBERTURA (
NombreCob VARCHAR(30) NOT NULL,
TelCob INTEGER NULL
CONSTRAINT positivo560
CHECK (TelCob >= 1),
DirCob VARCHAR(30) NULL,
CONSTRAINT XPKCOBERTURA
PRIMARY KEY (NombreCob)
);


CREATE TABLE PARTICIPANTE (
NroDoc INTEGER NOT NULL
CONSTRAINT positivo561
CHECK (NroDoc >= 1),
NombreCob VARCHAR(30) NULL,
NyAp VARCHAR(30) NOT NULL,
Dir VARCHAR(30) NOT NULL,
Tel INTEGER NULL
CONSTRAINT positivo562
CHECK (Tel >= 1),
Mail VARCHAR(30) NULL,
Localidad VARCHAR(30) NOT NULL,
Pcia VARCHAR(30) NOT NULL,
CodPostal VARCHAR(10) NULL,
Sexo CHAR(1) NOT NULL
CONSTRAINT sexo49
CHECK (Sexo = 'f' or Sexo = 'm'),
Edad SMALLINT NOT NULL
CONSTRAINT positivo563
CHECK (Edad >= 1),
CONSTRAINT XPKPARTICIPANTE
PRIMARY KEY (NroDoc),
CONSTRAINT posee
FOREIGN KEY (NombreCob)
REFERENCES COBERTURA
);

create trigger tI_PARTICIPANTE after INSERT on PARTICIPANTE for each row
declare numrows INTEGER;
begin
insert into COBERTURA (NombreCob)
select NombreCob
from PARTICIPANTE
where
:new.NombreCob is not null and
not exists (
select * from COBERTURA
where
:new.NombreCob = COBERTURA.NombreCob
);
end;
/

Inserting...

SQL> INSERT INTO PARTICIPANTE (NroDoc, NombreCob, NyAp, Dir, Tel, Mail, Localidad, Pcia, CodPostal,
Sexo, Edad)
2 values (21, 'nomcob', 'nyap1', 'dir1', 23, 'mail1', 'loca1', 'pci', 7000, 'f', 23);
INSERT INTO PARTICIPANTE (NroDoc, NombreCob, NyAp, Dir, Tel, Mail, Localidad, Pcia, CodPostal, Sexo,
*
ERROR at line 1:
ORA-04091: table SYSTEM.PARTICIPANTE is mutating, trigger/function may not see
it
ORA-06512: at "SYSTEM.TI_PARTICIPANTE", line 3
ORA-04088: error during execution of trigger 'SYSTEM.TI_PARTICIPANTE'

What´s the problem?
Then I drop the trigger and I create the following trigger:

create trigger tI_PARTICIPANTE after INSERT on PARTICIPANTE for each row
declare numrows INTEGER;
DECLARE Y VARCHAR(20);
begin
insert into tmp_participante VALUES (:NEW.NombreCob);
CURSOR C IS SELECT DISTINCT NombreCob FROM tmp_participante;
OPEN C;
FETCH C INTO Y,
WHILE C%found LOOP
insert into COBERTURA (Y)
where
Y is not null and
not exists (select * from COBERTURA where Y = COBERTURA.NombreCob);
FETCH C INTO Y
END LOOP;
CLOSE C;
DELETE FROM tmp_presentacion;
end;
/
Warning: Trigger created with compilation errors.


What´s the problem? Which are the possible reasons of this warning?

You cannot reference the trigger table within a FOR EACH ROW trigger.

In this case, I think you can simply remove the "for each row" clause from the trigger definition and modify the DML like this:

This will "fix up" the COBERTURA table for every row that is missing.

If that is not desirable (i.e. if you must ONLY "fix up" COBERTURA for the new values) then you need to do the standard "mutating table" work around (which involves a package and several triggers) described in detail here:

http://asktom.oracle.com/~tkyte/Mutate/index.html

hi,

to avoid the mutating table problem, try the following:

create a procedure with a identification parameter and in the declaration pragma autonomous_transaction and a cursor selecting the row from the source table, identified by the parameter. Then after begin, open the cursor, fetch it and insert the fetched data into the target table.
Do not forget commit.

good luck

Using autonomous_transaction to get round the mutating problem is a bad idea. Yes, the mutating table problem goes away - but so does data integrity! If the original INSERT is rolled back, the autonomous transaction will not be. There will be phantom records in COBERTURA.