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).

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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.

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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.