Setting IsPrimaryKey=true on column in table with no primary key

I'm writing a quick app using LINQ to SQL to populate a db with some test data and had a problem because one of the tables had no primary key as described by this bloke Can't Update because table has no primary key.

Taking the top answer I added the IsPrimaryKey attribute to an appropriate column and the app worked even though the I haven't开发者_StackOverflow社区 changed the db table itself (i.e. there is still no primary key).

I expect it will be ok for my current intentions but are there any side effects which may come from having a table without a primary key seen as having one by the LINQ object?

(I can only think it might be a problem if I tried to read from a table (or populate to a table) with data where the 'primary key' column has the same value in more than one row).

When using an ORM framework, you can simulate keys and foreign keys at ORM level, thus "hiding and overriding" the database defined ones.

That said, that's a practice that I wouldn't recommend. Even if the model is more important than the database itself, the logical structure should always match. It is ok doing what you did if you're forced to work with a legacy database and you don't have the possibility to fix it (like adding the PK on the table). But try to walk the righteous path everytime you can :)

Tables without a PK = Pure Evil.

Basically if all the table updates go through the LINQ object you should be fine. If you have a DBA that decides to modify data directly though SQL then you can quickly run into issues if he duplicates a row with the same PK value.