Question

I am running this query:

SELECT u.id as id, 
       COUNT(DISTINCT YEAR(TIMESTAMP), WEEK(TIMESTAMP)) cc, 
       GROUP_CONCAT(DISTINCT YEAR(TIMESTAMP),'-',WEEK(TIMESTAMP)) a
FROM   users u 
       JOIN checkins c 
         ON c.userid = u.id 
GROUP  BY userid
HAVING COUNT(cc) = 3

And this produces the following results:

id  cc  a
05  3   2010-43,2010-47,2010-45 
06  2   2010-44,2010-45 
13  3   2010-43,2010-45,2010-48 
20  3   2010-45,2010-43,2010-47 
21  3   2010-43,2010-47,2010-45 
22  2   2010-47,2010-48 
25  3   2010-48,2010-43,2010-46 
27  2   2010-42,2010-47 
30  2   2010-48,2010-45 
41  3   2010-44,2010-45,2010-47 
44  2   2010-42,2010-44 
50  2   2010-44,2010-47 
52  2   2010-48,2010-47 
57  2   2010-43,2010-44 
71  3   2010-43,2010-48,2010-47 
72  2   2010-43,2010-44 
78  3   2010-47,2010-42,2010-43 
79  2   2010-45,2010-46 
80  2   2010-46,2010-44 
87  1   2010-46 
97  1   2010-48 
108 3   2010-43,2010-47,2010-45 

As you see the cc column has values 2, 3, or even 1.

How that comes, when I’ve told with HAVING that should be 3?

Answer 1

MySQL does allow aliases in the Having clause. You would need to use:

HAVING cc = 3

not

HAVING COUNT(cc) = 3

in order to filter the results to only include rows which have a cc value of 3 though. I’m actually quite unsure though why HAVING COUNT(cc) = 3 would return any results at all.