LU08d – Fremdschlüssel nachträglich hinzufügen (ALTER TABLE)

Falls deine Tabellen schon ohne FK existieren, rüstest du die Constraints so nach:

ALTER TABLE Country
  ADD CONSTRAINT fk_country_continent
  FOREIGN KEY (ContinentID)
  REFERENCES Continent(ContinentID)
  ON DELETE RESTRICT
  ON UPDATE RESTRICT;
 
ALTER TABLE Trip
  ADD CONSTRAINT fk_trip_country
  FOREIGN KEY (CountryID)
  REFERENCES Country(CountryID)
  ON DELETE RESTRICT
  ON UPDATE RESTRICT;

Tipp: Effektive Constraint-Namen anzeigen:

SHOW CREATE TABLE Country\G
SHOW CREATE TABLE Trip\G