mysql-数据库中的关系表有什么作用 求大神解惑
mysql数据库
其中一张表叫做关系表，它内部只有两个字段，但全是id,一个是cid,一个是uid
其中两个id都是其他表的主键 我只想问这样记录下他们的id有什么用 或者 说这样关系表存在的意义是什么啊 真心求大神解答
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