Why Am I Getting MySQL Foreign Key Error 1005 (errno 150)?

Understanding MySQL Foreign Key Error 1005

When creating a foreign key constraint, MySQL encounters an error 1005 accompanied by an "errno 150" message. This error typically arises when the referenced table lacks a usable index that aligns with the referenced columns.

Answering Your Questions:

1. Can a Primary Key also serve as a Foreign Key?
   No, a primary key cannot serve as a foreign key for the same table, as it would result in circular referencing.
2. Addressing the MySQL Error:
   The error message suggests that the "dbimmobiliCondoni" table is missing an index on the referenced columns. To resolve this, you should create the following index on the "dbimmobiliImmobile" table:

CREATE INDEX idx_immobile ON dbimmobili.Immobile (ComuneImmobile, ViaImmobile, CivicoImmobile, InternoImmobile);

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