One to one Relationship

Hi,
I am new to Firebird RDBMS and I want to use Firebird database in my VisualStudio projects, with the support of Microsoft Entity Framework.
Since in my projects, luckily due to the Entity Framework, I don't have to learn the syntax of the Firebird SQL Commands, I used Firebird Maestro to create my database.
Now I have a problem: I need to create a one-to-one relationship between two tables, but Firebird Maestro allows me to create only a Foreign Key, which sets up a one-to-many relationship.
What may I do? May someone give me at least some information about how to create a one to one relationship by SQL statements?
Thanks!!

Give the Foreign Key field a unique index.

Why do you want a one to one?

There are two tables, Bill Entries (which stores the entries of the bills, by which you can also buy a cupon) and Cupons.
When I have a Bill Entry which is related to the purchase of a cupon, I need to bind that entry with a single entry of the table Cupons. I need to keep the two tables separated.


May you kindly explain me better? When I set up a Foreign Key, I may set the following fields: Foreign Colum (in the referencing table), Foreign Table, Foreign Table Columns, Update and Delete rule.

I did not mean to confuse you.
Set up a unique index on the same field as the foreign key.
The unique index will prevent the database ffrom accepting duplicate values.

However, unless there is some strong reason to do otherwise, I would suggest making that field the Primary Key in both tables and then add the foreign key constraint.
That would be a superior design.

Clive

In my case it's impossible, since the Bill Entries Table has as primary key the ID of the entry, it wouldn't make sense to set the "CuponId" as Primery Key.
Thanks for help, I will give a try tomorrow.

For the record. I did not say make CouponId the PK in both tables
Make the bill entry PK the PK of the coupons table (and drop the couponId field from the bill entries table).

Of course, you know your situation better than me. I am talking about a better technical schema design.

Clive