Question

I have a syntax issue with my use of GROUP_CONTACT.

With a sql statement that looks like this:

SELECT 

     s.school_code
    , s.school_name
    ,st.subject
    ,sg.subgroup
    ,GROUP_CONCAT(IF(r.year=2012,a.proficiency_index,NULL)) AS pi_2012
    ,GROUP_CONCAT(IF(r.year=2013,a.proficiency_index,NULL)) AS pi_2013

FROM 
    ayp_data a
        INNER JOIN 
            report_year r ON
                a.report_year_id = r.id
        INNER JOIN
            school s ON
                a.school_code_id = s.id
        INNER JOIN
            sub_group sg ON
                a.subgroup_id = sg.id
        INNER JOIN
            `subject` st ON
                a.subject_id = st.id

GROUP BY
      report_year_id,
      s.school_code
    , s.school_name
    ,st.subject
    ,sg.subgroup
HAVING 
s.school_name = 'Moody Elementary School' AND 
`subject` = 'Mathematics' AND 
`subgroup` = 'All Students'

I am getting results like this:

SCHOOL_CODE     SCHOOL_NAME     SUBJECT     SUBGROUP    PI_2012     PI_2013
0065    Moody Elementary School     Mathematics     All Students    9.640000343322754   (null)
0065    Moody Elementary School     Mathematics     All Students    (null)  10.920000076293945

I want to merge the two rows into one and put non-null field values PI_2012 and PI_2013 on the same line.

I thought I could do that with GROUP_CONTACT; but it’s not doing as I thought it would.

How could I use GROUP_CONCAT to merge these fields?

Or, is there an even smarter way to do this?

I have the full schema and query here on SQL Fiddle.

Answer 1

If you don’t want separate years to appear in separate rows, then you need to remove report_year_id from the GROUP BY clause. That is — you need to change this:

GROUP BY
      report_year_id,
      s.school_code
    , s.school_name
    ,st.subject
    ,sg.subgroup

to this:

GROUP BY
      s.school_code
    , s.school_name
    ,st.subject
    ,sg.subgroup