Re: Primary and foreign key

[Trudy Pelzer]

Bonjour Vanessa,

The explanation for the problem you are experiencing is that a FOREIGN
KEY must exactly match the columns of the referenced PRIMARY KEY.
In your third table, you are attempting to create:

FOREIGN KEY (`num_contact`) REFERENCES `societes_contacts` (`num_societe`,`num_contact`)

which is illegal SQL syntax.

The rules are:
- The number of columns that make up a FOREIGN KEY must match the
number of columns in the referenced PRIMARY KEY
- The data type of each column in the FOREIGN KEY must be the same
as the data type of the matching referenced PRIMARY KEY column.

Also, as Mr Bouman points out, the storage engine used must be InnoDB.

Trudy Pelzer, Engineering Project Manager
MySQL AB, www.mysql.com

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