SorryButImaNewbie

SQL multiple columns from one

2 posts in this topic

Hello!

I tried to post my question to stackoverflow, but couldn't (unknown error massage) and w3school, but i still need to be validated there to ask.

I'm trying to create a query (in SQL developer), which retruns the number of emission classes of cars, grouped by country codes. I can create it for one emission class like this:
 
  SELECT
      DISTINCT country_code,
      COUNT(emission_class) EURO0
    FROM
      DB.CUSTOMER_VEHICLE
    WHERE emission_class = 'E0'
    GROUP BY country_code;
My problem that I don't know how to count for a new column for example EURO1 emission class, from the same column (emission_class). I thought that I should create views and then add them togeather, or UNION 6 different selects. Tried with where and having clauses.
 
I always seems to run into some kind of a problem, then i realize that when I'm not sure how to start something properly, I should ask/research it first, so here I'm.
 
Thank you for the insight! (sorry still quite fresh with SQL, thank god I haven't paid anything for university, the internet is actually way better :) )

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I found a very good and simple solution, basicly just have to ask for the columns the right way :) 

SUM(CASE WHEN emission_class = 'E0' THEN 1 ELSE 0 END) AS EURO0

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