Compound key

[McG]

High school problem (I'm the teacher). A table contains cub no, date and badge no. Students have correctly identified compound key of cub no and badge no (e.g. 99-47 and 05). They know the key has to be unique when implemented in Filemaker pro. The problem - how to make a compound key unique. Have created a calculation field concatenating cub no and badge no but this does not allow validation checks to be applied. Have created a new field with content created by calculation much as above, and with unique validation applied - does not work as duplicate values are simpy ommited in new field.

Students MUST implement the solution using cub no and badge no - it is not acceptable to use a surrogate key, say, by creating a unique field with values such as 99-4705 entered directly.

Any solutions greatly received.

[comment]

Have created a new field with content created by calculation much as above, and with unique validation applied - does not work as duplicate values are simpy ommited in new field.

Huh? What do you mean omitted? How do they get omitted? That doesn't seem right, and the method should work, see the demo in this thread.

BTW, compound keys are no longer necessary in version 7, although you do need to create the calc if you want to validate uniqueness.