Prevent Duplicate Child Records?

[fishtek]

I have a station ID table connected to another data (species code) table via one to many relationship using the station ID. Users enter species codes for a station using a form. How can I prevent a user from entering duplicate species codes for a particular station ID. In other words its ok to have duplicate species codes in the data table, but not for a particular station ID. Hope this is not confusing. Thanks for any help.

 

[Andrzejek]

Would "one to one relationship" do the trick?

Have fun.

---- Andy

 

[PHV]

Create a unique index on (station ID,species code).
In fact, IMHO this should be the PK of the child table ...

Hope This Helps, PH.
FAQ219-2884
FAQ181-2886

 

[johnherman]

3 tables.

Station Table
- StationID
- other station data
Species Table
- SpeciesID
- other species data
Station-Species Table
- StationID
- SpeciesID

This allows a species to be recorded at more than one station, but not more than once at each station. The concept is called a relation table, bridge table, and I think there are a few other names.

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The reasonable man adapts himself to the world. The unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man. - George Bernard Shaw

 

[PHV]

johnherman, the OP clearly states a one-to-many Relationship.
Your suggestion of a junction table is suitable for a many-to-many Relationship.

Hope This Helps, PH.
FAQ219-2884
FAQ181-2886