我可以对sql中的不同表使用相同的外键吗

Question

假设我正在为教师创建投票系统，并希望将voting_id作为两张桌子的老师和高级教师的主键，并且将voting_id成为新桌子中两个桌子的单个外键，那么我可以选民吗？

Answer 1

Why do you want to have separate tables for teachers and senior teachers? It seems highly likely that those are really the same entity that should be modeled with a single teacher table that has a senior_teacher attribute. You would then create a voter table with a teacher_id column that refers to the teacher_id primary key in the teacher table. It doesn't make sense for the primary key of the teacher table to be voter_id rather than teacher_id .

Answer 2

I would model it differently. Teacher can have N votes(1:N relation). So the votes table has teacher_id, probably a grade and timestamp. I would put teacher and senior teacher in the same table and add a type column to it(senior or normal), because senior teacher is just an extended type of a teacher.

Voting_id can't be primary key because it identifies vote not the teacher. Also you would have collisions because teacher and senior teacher can have the same primary id if they are in two seperate tables.