Nothing special needs to be done with the foreign key fields in the join table as they will get populated with data from the other two tables as records are created. Each record in the “join table” would have the foreign key fields of the two tables it is joining together. Using a third table, commonly called a “join table”, does this.
To get around the problem of having a many-to-many relationship you need to break apart the many-to-many relationship into two one-to-many relationships. If there were “many” invoices with the same invoice number and one of your many customers called up asking about that invoice number how would you know which specific one they were referring to? The answer is you could not.
Consider the example of keeping track of invoices. According to FileMaker’s Help page on Join Tables, “In relational database design, a many-to-many relationship is not allowed.
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