如何在保持参照完整性的父记录中识别“首选”子项？

I am defining an entity which represents a Page which consists of one or more Part items. Every Page must have at least one Part defined. Each Part belongs to only one Page. One of the Part items will be the "master" Part on the page, and all others will rely on the master. Other than this difference, the master and slave parts behave identically.I am defining an entity which represents a Page