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  1. #1
    Join Date
    Jan 2010

    Cool Unanswered: Microsoft SQL Server 2008 Constraints ?

    Hi All,

    This is my first post in this forums.

    Does SQL Server 2008, have any limitations in accepting
    explicitly declared multiple foreign keys, example as follows :

    CREATE TABLE PracticalSession
    StudentNo CHAR(5), /* Belongs To Trainees Table */
    EmployeeNo CHAR(4), /* Belongs To DrivingInstructors Table */
    RegistrationNo CHAR(6), /* Belongs To Vehicles Table */
    PracticalDate DATE,
    StartTime TIME

    PK (PracticalDate, StartTime, StudentNo, EmployeeNo, RegistrationNo),
    FK (StudentNo) REFERENCES Trainees (StudentNo)
    FK (EmployeeNo) REFERENCES DrivingInstructors (EmployeeNo)
    FK (RegistrationNo) REFERENCES Vehicles (RegistrationNo)

    Scenario : When a student goes for a driving lesson, the student and instructor are assigned to a vehicle.

    Thanks in Advance.

  2. #2
    Join Date
    Nov 2005
    Read here: FOREIGN KEY Constraints

    I'm not sure if the 253 limit is a best practise or if SQL Server will throw an exception when creating the 254th fk constraint.

  3. #3
    Join Date
    Dec 2007
    London, UK
    Multiple foreign keys are perfectly OK. The main restriction is that columns in the constraint must exactly match the list of columns in a UNIQUE or PRIMARY KEY constraint or unique index.

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