Preventing duplicates

[waka]

I have a database that links individual trees to a plot. The tree table has a tree_number field that contains a numeric tag number. I'm trying to figure out a way to restrict the tag number so that duplicate numbers can not be entered in the same plot. Is this possible?

Thanks!

 

[HiTechCoach]

Sure. I would create a compound index on the two fields for the plot and tag number that is set to no dups allowed.

 

[RossWindows]

You will have to create an indexed (no duplicates) field in the plot table that contains a combination of treeID and PlotID.
You can't use Autonumber for this obviously, so you'll have to use code to create this compound-key.

It may look something like this "1234_0012" where 1234 is the Tree ID and 0012 is the Plot ID (or vis-versa)

Ah, beat me to it.

 

[RossWindows]

But wait, let me ask you this;

Can a single tree be in two plots at once? ever?