CREATE TABLE [dbo].[PrincipalGrouping] (
    [Groups_PrincipalID]  INT NOT NULL,
    [Members_PrincipalID] INT NOT NULL,
    CONSTRAINT [PK_PrincipalGrouping] PRIMARY KEY CLUSTERED ([Groups_PrincipalID] ASC, [Members_PrincipalID] ASC),
    CONSTRAINT [FK_PrincipalGrouping_Groups] FOREIGN KEY ([Members_PrincipalID]) REFERENCES [dbo].[Principal] ([PrincipalID]),
    CONSTRAINT [FK_PrincipalGrouping_Members] FOREIGN KEY ([Groups_PrincipalID]) REFERENCES [dbo].[Principal] ([PrincipalID])
);
GO

CREATE NONCLUSTERED INDEX [IX_FK_PrincipalGrouping_Groups]
    ON [dbo].[PrincipalGrouping]([Members_PrincipalID] ASC);
GO