I have two tables:

```
CREATE TABLE Order (
    orderId INTEGER IDENTITY NOT NULL,
    PRIMARY KEY (orderId) 
)

CREATE TABLE OrderAdditionalDetails (
    additionalDetailsId INTEGER IDENTITY NOT NULL,
    orderId INTEGER NOT NULL,
    PRIMARY KEY (additionalDetailsId),
    FOREIGN KEY (orderId) REFERENCES Order(orderId)
)

```

I have a Foreign key (FK\_OrderAdditionalDetails\_Order) declared on the OrderAdditionalDetails table, on the orderId field. I also have a 'unique' constraint on the orderId field in the OrderAdditionalDetails table. The idea is that each 'order' will have zero or one entries in the 'OrderAdditionalDetails' table.

This all picked up by the entity framework model file, however when I try to create the Navigation property, it only lets me declare a 1 to many relationship. The error I get is as follows:

Running transformation: Multiplicity is not valid in Role 'OrderAdditionalDetails' in relationship 'FK\_OrderAdditionalDetails\_Order'. Because the Dependent Role properties are not the key properties, the upper bound of the multiplicity of the Dependent Role must be \*.

I'm really not sure what this means - googling the error did not prove helpful. Can anybody shed some light on what I am doing wrong?