Question

Is there a way for SQL to enforce unique column values, that are not a primary key to another table?

For instance, say I have TblDog which has the fields:

1. DogId – Primary Key
2. DogTag – Integer
3. DogNumber – varchar

The DogTag and DogNumber fields must be unique, but are not linked to any sort of table.

The only way I can think of involves pulling any records that match the DogTag and pulling any records that match the DogNumber before creating or editing (excluding the current record being updated.) This is two calls to the database before even creating/editing the record.

My question is: is there a way to set SQL to enforce these values to be unique, without setting them as a key, or in Entity Frameworks (without excessive calls to the DB)?

I understand that I could group the two calls in one, but I need to be able to inform the user exactly which field has been duplicated (or both).

Edit: The database is SQL Server 2008 R2.

Answer 1

I’d suggest setting unique constraints/indexes to prevent duplicate entries.