How do you create a foreign key relationship in a SQL Server CE (Compact Edition) Database?

Question

Unfortunately there is currently no designer support (unlike for SQL Server 2005) for building relationships between tables in SQL Server CE. To build relationships you need to use SQL commands such as:

ALTER TABLE Orders
ADD CONSTRAINT FK_Customer_Order
FOREIGN KEY (CustomerId) REFERENCES Customers(CustomerId)

If you are doing CE development, i would recomend this FAQ:

EDIT: In Visual Studio 2008 this is now possible to do in the GUI by right-clicking on your table.

Visual Studio 2008 does have a designer that allows you to add FK's. Just right-click the table... Table Properties, then go to the "Add Relations" section.

You need to create a query (in Visual Studio, right-click on the DB connection -> New Query) and execute the following SQL:

ALTER TABLE tblAlpha
ADD CONSTRAINT MyConstraint FOREIGN KEY (FK_id) REFERENCES
tblGamma(GammaID)
ON UPDATE CASCADE

To verify that your foreign key was created, execute the following SQL:

SELECT * FROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS

Credit to E Jensen (http://forums.microsoft.com/MSDN/ShowPost.aspx?PostID=532377&SiteID=1)

Alan is correct when he says there's designer support. Rhywun is incorrect when he implies you cannot choose the foreign key table. What he means is that in the UI the foreign key table drop down is greyed out - all that means is he has not right clicked on the correct table to add the foreign key to.

In summary, right click on the foriegn key table and then via the 'Table Properties' > 'Add Relations' option you select the related primary key table.

I've done it numerous times and it works.

create table employee
(
   empid int,
   empname varchar(40),
   designation varchar(30),
   hiredate datetime, 
   Bsalary int,
   depno constraint emp_m foreign key references department(depno)
)

We should have an primary key to create foreign key or relationship between two or more table .