I have created tables in MySQL Workbench as shown below :
ORDRE table:
CREATE TABLE Ordre (
OrdreID INT NOT NULL,
OrdreDato DATE DEFAULT NULL,
KundeID INT DEFAULT NULL,
CONSTRAINT Ordre_pk PRIMARY KEY (OrdreID),
CONSTRAINT Ordre_fk FOREIGN KEY (KundeID) REFERENCES Kunde (KundeID)
)
ENGINE = InnoDB;
PRODUKT table:
CREATE TABLE Produkt (
ProduktID INT NOT NULL,
ProduktBeskrivelse VARCHAR(100) DEFAULT NULL,
ProduktFarge VARCHAR(20) DEFAULT NULL,
Enhetpris INT DEFAULT NULL,
CONSTRAINT Produkt_pk PRIMARY KEY (ProduktID)
)
ENGINE = InnoDB;
and ORDRELINJE table:
CREATE TABLE Ordrelinje (
Ordre INT NOT NULL,
Produkt INT NOT NULL,
AntallBestilt INT DEFAULT NULL,
CONSTRAINT Ordrelinje_pk PRIMARY KEY (Ordre, Produkt),
CONSTRAINT Ordrelinje_fk FOREIGN KEY (Ordre) REFERENCES Ordre (OrdreID),
CONSTRAINT Ordrelinje_fk1 FOREIGN KEY (Produkt) REFERENCES Produkt (ProduktID)
)
ENGINE = InnoDB;
so when I try to insert values into ORDRELINJE
table i get:
Error Code: 1452. Cannot add or update a child row: a foreign key constraint fails (
srdjank
.Ordrelinje
, CONSTRAINTOrdrelinje_fk
FOREIGN KEY (Ordre
) REFERENCESOrdre
(OrdreID
))
I've seen the other posts on this topic, but no luck. Am I overseeing something or any idea what to do?
Taken from Using FOREIGN KEY Constraints
Foreign key relationships involve a parent table that holds the central data values, and a child table with identical values pointing back to its parent. The FOREIGN KEY clause is specified in the child table.
It will reject any INSERT or UPDATE operation that attempts to create a foreign key value in a child table if there is no a matching candidate key value in the parent table.
So your error Error Code: 1452. Cannot add or update a child row: a foreign key constraint fails
essentially means that, you are trying to add a row to your Ordrelinje
table for which no matching row (OrderID) is present in Ordre
table.
You must first insert the row to your Ordre
table.