1 of 7
Hannah Vernon
  • 66.4k
  • 22
  • 155
  • 292

Why is Grandparent -> grandchild not valid?

This seems to me to be fully valid; even if it does mean an extra 4 bytes per row to store the grandparent id in the grandchild row.

You could use an extra whole table to define the relationship, but that looks like it would be even less efficient to me, and would needlessly complicate the design.

Hannah Vernon
  • 66.4k
  • 22
  • 155
  • 292