Calc field ok for relational Key?

[J__]

Hi,

I'm pretty sure this is ok, but just want to verify with the experts.

I have a field called Task Number, it looks something like this 2005-0021-0024

A project is related to a Task record and I have made the TaskID a composite of the Project ID, the project ID part is 2005-0021 and the taskID part is 0024

is it ok to create a calculated field, say called ProjectID_Calc, which is maybe Left(TaskID; 6)

so the projectID_Calc for the above number will be 2005-0021

is there any harm or overhead/performance problems with doing that?

it seems "mostly harmless", but i want to be sure.

thanks for your help in advance.

sincerely,

j__

[RalphL]

The usual concerns about key fields. The primary key must be unique. The foreign key must be indexed. Also you can not use auto create related record if the foreign key is a calculation.

[J__]

Thanks Ralph,

The primary key is unique ... foreign key indexed.. ok. .. uh .. oooh... gotcha.. :^)

OK, I'll use another approach.

thanks for the info,

sincerely,

j__

[CobaltSky]

Also you can not use auto create related record if the foreign key is a calculation.

...that is, unless it is an auto-enter calculation!