Preserving History

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Hi gang:

To further the Garbage Collection thread on to another level (i.e., preserving history) please consider this:

Okay, let's say we have a table containing all the instances of tutors teaching courses. A record might look like this:

Course-to-Tutor table
course_id = 123
tutor_id = 7
date_active = 2/4/9
date_inactive = null

The above record was assembled from the following recrods:

Tutor table:
id = 7
name = joe

Course table:
id = 123
title = Introduction to Moonshine

Okay, so let's now delete the course "Introduction to Moonshine"!

At the first opportunity to search the Course-to-Tutor table we find that the course 123 is now absent from our database and as such we set the date_inactive field -- it won't be considered again.

Okay, so what does that tell us about the history? It only provides that at one time joe taught an undefined course. Furthermore, if joe quits, then we only have a record that says someone with an id of 7 taught a course with an id of 123 -- that doesn't make much sense, does it?

Now, if we reconsider the Course-to-Tutor table and instead of putting in the tutor_id and course_id, we put in the actual name of the tutor and title of the class, then at least we have a history that makes sense.

However by doing that, we violate the primary principle of a relational database by creating redundant data.

I guess that one can say that if we never actually delete the tutor nor the course, but instead just make them inactive as well, then we have solved the problem -- is that the answer?

In any event, what problems do you foresee if I used the actual names and titles for the Course-to-Tutor table instead of their id's? After all, the instance records would retain a simple history of what happened regardless of deletions AND a search for "Introduction to Moonshine" should be essentially as fast as a search for "123" if both fields are indexed, am I right or wrong?

Cheers,

tedd

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