我有4个关系A,B,C和D,每个关系包含一个字段id(与其他字段)。我希望INNER在id上加入这些关系,这样最终关系应该只有id,它们是所有A,B,C和D关系的一部分。我可以通过多种方式做到这一点:
1. X = JOIN A BY id, B BY id, C BY id, D BY id;
2. X = JOIN A BY id, B BY id;
Y = JOIN C BY id, D BY id;
Z = JOIN X BY A::id, Y BY C::id
3. X = JOIN A BY id, B BY id;
Y = JOIN X BY B::id, C BY id;
Z = JOIN Y BY C::id, D BY id;
我如何决定上述哪种方式最具表现力。在选择上述方法之一之前,我需要考虑的所有事情(例如A..D的大小,最终关系中每个A..D所需的列数等)?