CONSTRAINT FK_A_B   FOREIGN KEY(A_Key)
        REFERENCES B(B_Key),

CONSTRAINT FK_B_A   FOREIGN KEY(B_Key)
        REFERENCES B(A_Key),

CREATE TABLE [Person](

    [PersonID] [int] PRIMARY KEY NOT NULL,
    [FirstName] varchar(20) NOT NULL,
    [MiddleName] varchar (20) NULL,
    [LastName] varchar(20) NOT NULL,

)

CREATE TABLE [PersonInfo](

    [PersonID] [int] FOREIGN KEY REFERENCES [dbo].[Person] (PersonID) NOT NULL,
    [Phone] varchar(20) NOT NULL,
    [Email] varchar (20) NULL,
    [Address] varchar(20) NOT NULL,
)