After insert trigger causing mutating table error - sql

Question

Create table statements:
CREATE TABLE Client(
nclient INT NOT NULL,
nom VARCHAR(45) NOT NULL UNIQUE,
plafond NUMERIC(10,2) DEFAULT 0,
CHECK (plafond>=0),
CONSTRAINT PK_Client PRIMARY KEY (nclient)
);
CREATE TABLE Compte(
ncompte INT NOT NULL,
solde NUMERIC(10,2),
ouvert NUMERIC(1) DEFAULT 1,
nbessais INT,
code Numeric(4),
nclient NUMERIC(4),
CONSTRAINT PK_Compte PRIMARY KEY (ncompte),
CONSTRAINT FK_Compte_nclient_Client FOREIGN KEY (nclient) REFERENCES Client(nclient),
CONSTRAINT CK_solde CHECK (solde>=0),
CONSTRAINT CK_ouvert CHECK(ouvert between 0 and 1),
CONSTRAINT CK_code CHECK (code>0)
);
CREATE TABLE Operation(
noperation INT NOT NULL,
dateoperation DATE Default SYSDATE,
codepropose NUMERIC(4),
montant NUMERIC(10,2),
ncompte INT,
CONSTRAINT PK_Operation PRIMARY KEY (noperation),
CONSTRAINT FK_Ope_ncompte_Compte FOREIGN KEY (ncompte) REFERENCES Compte(ncompte),
CONSTRAINT CK_codepropose CHECK (codepropose>=0),
CONSTRAINT CK_montant CHECK (montant>=0)
);
CREATE TABLE Historique(
nhistorique INT NOT NULL,
dateoperation DATE DEFAULT SYSDATE,
montant NUMERIC(10,2),
ncompte INT,
CONSTRAINT PK_Historique PRIMARY KEY (nhistorique)
);
CREATE TABLE Incident(
nincident INT NOT NULL,
message VARCHAR(45),
noperation INT,
CONSTRAINT PK_Incident PRIMARY KEY (nincident),
CONSTRAINT FK_Inc_noperation_Operation FOREIGN KEY (noperation) REFERENCES Operation(noperation)
);
Trigger code:
create or replace TRIGGER TRG_OPERATION_CARTE
AFTER INSERT OR UPDATE ON Operation
FOR EACH ROW
DECLARE
solde NUMBER := 0;
ouvert NUMBER := 0;
essai NUMBER := 0;
code NUMBER := 0;
plafondActuel NUMBER := 0;
decouvertAuth NUMBER := 0;
BEGIN
SELECT SUM(montant) INTO plafondActuel FROM Operation WHERE dateoperation >= SYSDATE - 7 AND ncompte = :NEW.ncompte;
SELECT plafond INTO decouvertAuth FROM Client Cl LEFT JOIN Compte Cp ON Cl.nclient = Cp.nclient WHERE Cp.ncompte = :NEW.ncompte;
SELECT solde, ouvert, nbessais, code
INTO solde, ouvert, essai, code
FROM Compte
WHERE Compte.ncompte = :NEW.ncompte;
IF ouvert = 0 THEN
INSERT INTO Incident (message,noperation) values ('Compte bloqué',:NEW.noperation);
ELSE
IF :NEW.codepropose = code THEN
IF (solde + decouvertAuth) > :NEW.montant THEN
IF (plafondActuel + :NEW.montant) > 300 THEN
INSERT INTO Incident (message,noperation) values ('Lopération dépasse le plafond authorisé',:NEW.noperation);
ELSE
INSERT INTO Historique (montant,ncompte) values (:NEW.montant,:NEW.ncompte);
END IF;
ELSE
INSERT INTO Incident (message,noperation) values ('Lopération dépasse le découvert authorisé',:NEW.noperation);
END IF;
ELSE
essai := essai + 1;
UPDATE Compte SET nbessais = essai WHERE Compte.ncompte = :NEW.ncompte;
IF essai >=3 THEN
UPDATE Compte SET ouvert = 0 WHERE Compte.ncompte = :NEW.ncompte;
INSERT INTO Incident (message,noperation) values ('Compte bloqué, 3 tentatives échouées',:NEW.noperation);
END IF;
END IF;
END IF;
END;
I am pretty sure that the algorithm and the Trigger are correct but I have an error :
Cause: A trigger (or a user defined plsql function that is referenced in this statement) attempted to look at (or modify) a table that was in the middle of being modified by the statement which fired it.
Action: Rewrite the trigger (or function) so it does not read that table.
Here are some tests, everything is ok apart from the last insert :
INSERT INTO Client (nom) values ('abderrahmane');
INSERT INTO Client (nom) values ('ben');
Select * FROM Client;
INSERT INTO Compte (solde,nclient) values (200,1);
INSERT INTO Compte (nclient,code) values (2,2403);
INSERT INTO Compte (solde,nclient) values (2300,3);
SELECT * FROM Compte;
INSERT INTO Operation (montant,ncompte) values (200,2);
INSERT INTO Operation (codepropose,ncompte) values (2010,2);
INSERT INTO Operation (ncompte) values (1);
INSERT INTO Operation (codepropose,montant,ncompte) values (2020,20,1);
INSERT INTO Operation (codepropose,montant,ncompte,dateoperation) values (2030,30,2,'01/01/2001');
INSERT INTO Operation (codepropose,montant,ncompte) values (2030,30,3);
SELECT * FROM Operation;
INSERT INTO Historique (montant,ncompte) values (200,2);
INSERT INTO Historique (dateoperation,ncompte) values ('15/04/16',2);
INSERT INTO Historique (ncompte) values (1);
INSERT INTO Historique (dateoperation,montant,ncompte) values ('15/04/16',20,1);
INSERT INTO Historique (dateoperation,montant,ncompte) values ('15/04/16',30,3);
SELECT * FROM Historique;
INSERT INTO Incident (message,noperation) values ('Incident 1',2);
INSERT INTO Incident (message,noperation) values ('Incident 2',8);
INSERT INTO Incident (message,noperation) values ('Incident 3',1);
SELECT * FROM Incident;
UPDATE Compte SET ouvert = 0 WHERE nclient = 2;
INSERT INTO Operation (montant,ncompte,codepropose) values (200,2,2403);
SELECT * FROM Incident;

Answer 1

Mutating Table error comes because your are using that particular table and making any kind of modification in the same table.
Since you are trying to select records from table in the trigger of the same table you are getting this error.

Answer 2

Thanks everyone for your answers, I just had to change the tablename, instead of taking the sum from operation, I took it from historique :
CREATE OR REPLACE TRIGGER TRG_OPERATION_CARTE
AFTER INSERT OR UPDATE ON Operation
FOR EACH ROW
DECLARE
solde NUMBER := 0;
ouvert NUMBER := 0;
essai NUMBER := 0;
code NUMBER := 0;
plafondActuel NUMBER := 0;
decouvertAuth NUMBER := 0;
BEGIN
SELECT SUM(montant) INTO plafondActuel FROM Historique WHERE dateoperation >= SYSDATE - 7 AND ncompte = :NEW.ncompte;
SELECT plafond INTO decouvertAuth FROM Client Cl LEFT JOIN Compte Cp ON Cl.nclient = Cp.nclient WHERE Cp.ncompte = :NEW.ncompte;
SELECT solde, ouvert, nbessais, code
INTO solde, ouvert, essai, code
FROM Compte
WHERE Compte.ncompte = :NEW.ncompte;
IF ouvert = 0 THEN
INSERT INTO Incident (message,noperation) values ('Compte bloqué',:NEW.noperation);
ELSE
IF :NEW.codepropose = code THEN
IF (solde + decouvertAuth) >= :NEW.montant THEN
IF (plafondActuel + :NEW.montant) > 300 THEN
INSERT INTO Incident (message,noperation) values ('Lopération dépasse le plafond authorisé',:NEW.noperation);
ELSE
UPDATE Compte SET solde = (solde - :NEW.montant) WHERE Compte.ncompte = :NEW.ncompte;
INSERT INTO Historique (montant,ncompte) values (:NEW.montant,:NEW.ncompte);
END IF;
ELSE
INSERT INTO Incident (message,noperation) values ('Lopération dépasse le découvert authorisé',:NEW.noperation);
END IF;
ELSE
essai := essai + 1;
UPDATE Compte SET nbessais = essai WHERE Compte.ncompte = :NEW.ncompte;
IF essai >=3 THEN
UPDATE Compte SET ouvert = 0 WHERE Compte.ncompte = :NEW.ncompte;
INSERT INTO Incident (message,noperation) values (CONCAT('Compte bloqué : tentative n° ', essai),:NEW.noperation);
ELSE
INSERT INTO Incident (message,noperation) values (CONCAT('Code erroné : tentative n° ', essai),:NEW.noperation);
END IF;
END IF;
END IF;
END;
/