Updated lesson 1 (novice sql) according to Greg's comment

Hi Luca!

I'll post some updates according to Greg's comment (https://github.com/swcarpentry/bc/pull/657#issuecomment-54817477). Here's the first commit.

As previously, this should automatically appear in your main PR (https://github.com/swcarpentry/bc/pull/657) as soon as you merge this PR.

One more commit will follow.