MERGE [dbo].[ReviewerGroupMemberships] AS T
    USING (VALUES (@ReviewerGroupId, @WorkspaceReviewerId)) AS S([ReviewerGroupId], [WorkspaceReviewerId])
    ON T.[ReviewerGroupId] = S.[ReviewerGroupId] AND T.[WorkspaceReviewerId] = S.[WorkspaceReviewerId]
    WHEN NOT MATCHED THEN
    INSERT ([ReviewerGroupId], [WorkspaceReviewerId])
    VALUES (S.[ReviewerGroupId], S.[WorkspaceReviewerId]);
