FAQ: Code Challenge: Queries - Code Challenge 9

This community-built FAQ covers the “Code Challenge 9” exercise from the lesson “Code Challenge: Queries”.

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I have a kind of general question. The timestamp values make no sense to me, so I didn’t understand why we need to put them in DESC order. Can someone explain what this number means so that I can understand why we ordered it this way?

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In this exercise we are asked to find 20 recent articles from Business category.

I want to go further and find 20 recent articles in both Business and Technology categories . Unfortunately, my query didn’t work:

select * from news
where category = ‘t’ or category = ‘b’
group by category
limit 20;

I also tried another variation of where like category = ‘t’ or ‘b’ - also didn’t work.

Also tried this

select * from news
group by category
having category = ‘b’ or category = ‘t’
limit 20;

How can I combine search for two categories and why my queries didn’t work?

If you want the 20 most recent articles, shouldn’t use order by?

`where category = ‘t’ or category = ‘b’` should work, or you could use: ` WHERE category IN ('b', 't')`.

Anyway, if we do:

``````select * from news
where category = ‘t’ or category = ‘b’
order by timestamp des;
``````

(which codecademy doesn’t like), we can see of all the most recent articles, they are all in tech, not Business.

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Is the IS operator the same as “=”? I thought = was only used from numbers, but then I saw it used instead of IS in the exercise. My query with IS worked, but I wasn’t sure what the rule/best practice is.

have you tried to google if `is` and `=` are the same thing? Understanding the difference is highly recommended.

Yes, I did Google it, but all of the answers I found are in relation to the NULL value. I thought that this forum was for questions on the exercises in Codecademy. Would appreciate some help on the concept.

So that answers the question? `=` checks for equality, `is` checks if value is a null value

we can’t use `=` for checking if value equals NULL, because null means no value.

OK, now I get it. IS only applies to NULL. Otherwise, = is the correct operator. Thank you.

1 Like