我正在尝试找出当外键基于类型指向不同表时如何正确存储外键。我searched但是nothing我foundseemed至helpatall.有一个表将存储学分的大部分基础知识:user_accounting--------------------user_accounting_id(PK)user_id(FK)amounttype(+deposit,+credit,-transfer,-purchase)credit(bool,soIdon'thavetoalwayscheckifamountis0)void(incaseitwascanceledandrepairedwithsome