Question

Have this query:

SELECT
  count(*) as Total, 
  SUM(CASE WHEN gender = 1 then 1 ELSE 0 END) Male, 
  SUM(CASE WHEN gender = 2 then 1 ELSE 0 END) Female, 
  SUM(CASE WHEN gender = 0 then 1 ELSE 0 END) Unknown, 
  CASE 
    WHEN age>2 AND age<15 THEN '2-15' 
    WHEN age>18 AND age<25 THEN '18-25' 
  END AS var
FROM
  persons 
WHERE
  1=1 
  AND `date` > '2012-01-10'
  AND `date` < '2013-01-07' 
GROUP BY 
  CASE 
    WHEN age>2 AND age<15 THEN '2-15' 
    WHEN age>18 AND age<25 THEN '18-25'
  END

And is resulting this:

Total Male  Female  Unknown var
29     17   12      0       NULL
7      0    7       0       18-25
3      0    3       0       2-15

1st question:
Why is this resulting that NULL ? What could be done to only show results with values?

2nd question:
mysql is ordering my var column with 18-25 before 2-15, migth be because of number 1 cames first then number 2. But the point is order that as numbers, and 2 came first then 18.

Cheers 🙂

Answer 1

1st answer:
It is NULL because it does not satisfy any of your CASE conditions for the age. Adding a clause to the WHERE like this should do it:

WHERE (age > 2 AND age < 15) OR (age > 18 AND age < 25)

2nd answer:
You are correct, it is ordering them by strings (because that is what they are). Just change the direction of the sort by doing ORDER ASC or ORDER DESC