Treffynnon

OK, so I think this might be a language/understanding difference here - perhaps what I have written isn't clear enough - not sure. The statement to some degree, in my opinion, doesn't imply that the key isn't actually unique. It still means unique.

What I meant is that if you don't have a unique column to make, say, a primary key with then you need to make it unique by adding (an)other column(s) to it in the key definition. Each additional column being a degree of difference/separation in my mind as I was writing it.

I hope that explanation makes sense and doesn't confuse the issue further.

I'd like to get your feedback on what you think it could say to make this clearer - I want to convey:

a. it must be unique.

b. you can have multi-column keys (some users - especially those tied to an ORM - don't actually know that you can do this).

Well that's good seeing as though I wrote the guide in the first place.

An illustration in bad pseudocode:

    PRIMARY KEY (account_number, transaction_date)

Have you read Celko's book? If not I suggest you do. As the guide states at the very top that is where you'll find the detail you're after.

This doesn't solve the problem at hand either unfortunately. You'll still have a hanging comma in front of `last_name`:

  SELECT 
      -- first_name
       , last_name
       , email_address
    FROM users

When parsed it will look like this query error to the system:

  SELECT
       , last_name
       , email_address
    FROM users

I think a lot of this comes down to what appears to be a simple misunderstanding.

Avoid - in this context means that where it does not make sense (for performance, readability, etc reasons) then don't follow the guide. Follow it where possible and be mindful of when you deviate that you're adding to tech debt.

Putting the comma before doesn't actually make commenting out columns easier - it just moves the problem to the other end of the list. Just try commenting out the first column in your SQL and you'll see what I mean.

I am totally lost when it comes to your comments on the second item. It seems you're trying to say that surrogate keys are easier to find or perhaps guess.

The indexes set out against a table can generally be accessed with a query making it very easy to work out what existing index suits your use case best.

Thinking multi-column indexes here.

Basically this is the answer - besides that bit about acquiescing to the demands of an ORM.

This seems to be a simple misunderstanding.

Try - in this context means where it doesn't make sense (for performance, readability, etc reasons) then don't follow the guide. Follow it where possible and be mindful of when you deviate that you're adding to tech debt.

This is a pretty commonly asked question. The answer is two fold:

1. putting the comma before doesn't actually make commenting out columns easier - it just moves the problem to the other end of the list. Just try commenting out `first_name` in your example and you'll see what I mean.

2. because normal convention would be for the comma to come immediately after an item in written English.

No, actually the collective of player isn't team in this case.

Not all players will be on the same team, but they still participate in the league so I disagree with this example terminology shift.

You would end up with a slightly more generalised naming like this in my opinion:

- athletes - teams - leagues

In this particular case there are no suitable collective terms.