SQL表中的两个条目之间的关联 [英] Association between two entries in SQL table

问题描述

假设您有一个存储人员列表的数据库表。你想建立人与人之间的关系，即我是朋友与人J的人。

我想在这种情况下，需要第二个表来存储人际关系。此表将包含两个字段（person1，person2），每个条目对应于两个人之间的一对一关系。

这是正确的还是有更多聪明的方式做到吗？这个方法使得关联表缩放为n_users ^ 2。

解决方案

多对多关系。这是所有人都可以有很多朋友。

如果你有一对多的关系，像所有人有一个老板（或没有老板），你不需要额外的表，那么在person表中只需要一个BossId列。

Imagine you have a database table that stores a list of people. You want to establish a relationship between peoples, i.e., person I is friend with person J.

I suppose in this case, one needs a second table to store people associations. This table would contain two fields (person1, person2) and each entry corresponds to a one-to-one relationship between two people.

Is that right or is there a more clever way to do it? This method makes the association table scale like n_users^2.

解决方案

Yes, this is right if you want to model a many-to-many relation. That is all persons can have many friends.

If you have a one-to-many relation, like all persons has one boss (or no boss) you don't need the extra table, then you only need a BossId column in the person table.

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