[Treffynnon]

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.

[r00fus]

Re; #1, I also use comma-first indenting and I actually put each field in it's own line specifically for ease in commenting (first_name would have its own line)

[Treffynnon]

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