Question

I had this query:

SELECT `name`, floor(max(score)), skill
FROM
  (SELECT k.`name`, s.`name` as skill, *long complex formula* as score
  FROM `keywords_skills` ks
  JOIN keywords k        ON k.id = ks.keyword_id
  JOIN skills s          ON s.id = ks.skill_id
  JOIN jobs_keywords jk  ON jk.keyword_id = k.id
  WHERE job_id = 87293) t1
GROUP BY `name`
ORDER BY `name` asc

obviously i want ‘skill’ to refer the same row as max(score), but I did not know how to make that happen. However, when I add an ORDER BY to the subquery like so:

SELECT `name`, floor(max(score)), skill
FROM
  (SELECT k.`name`, s.`name` as skill, *long complex formula* as score
  FROM `keywords_skills` ks
  JOIN keywords k        ON k.id = ks.keyword_id
  JOIN skills s          ON s.id = ks.skill_id
  JOIN jobs_keywords jk  ON jk.keyword_id = k.id
  WHERE job_id = 87293
  ORDER BY score DESC) t1
GROUP BY `name`
ORDER BY `name` asc

everything seems to work great! My question is: have I solved my problem or just implemented an unreliable hack that will haunt me later?

---

EDIT: perhaps I should have explain more what I was looking for:

Keywords and Skills are in a many-to-many relationship with each other. I am not looking simply for the keyword with the highest score, but the skill with the highest score for each keyword.

I also thought I could use LIMIT 1 somehow (perhaps in a subquery), but so far have not thought of a way to make it happen.

Answer 1

I think you are close with your first one… just add a LIMIT 1 in addition to the order by to put the highest skill first (order by column 3 which is your score formula

— PER REVISED CLARIFICATION…
I’m swapping around the query in hierarchy of the JOB ID in question, then finding ITs skills and keywords instead of the reverse — relying on keyword skills. In the case you want, you WILL need a nested query… Example:

Job A has Keywords
   Word A
       Skill A-1    Score:90  (you want this one)
       Skill A-2    Score:70
       Skill A-3    Score:60
   Word B 
       Skill B-1    Score:30
       Skill B-2    Score:20
       Skill B-3    Score:95  (you want this one)
       Skill B-4    Score:80
   Word C 
       Skill C-1    Score:10
       Skill C-2    Score:20
       Skill C-3    Score:30  (you want this one)

The inner query should ONLY include the keyword id and the maximum score for the keyword — all associated with the one Job_ID in questino. THEN, re-join again, but this time, we no longer need he job_keywords as each K.ID and name description are IN the prequery. Then, just need to re-join to the skills matching the qualifying SCORE.

SELECT STRAIGHT_JOIN
      PreQuery.Keyword, 
      s.name as Skill, 
      PreQuery.Score
   from
      ( SELECT STRAIGHT_JOIN
              k.id,
              k.name Keyword, 
              max( s.Score ) maxScore
           from
              jobs_keywords jk
                 join keywords k 
                    on jk.keyword_id = k.id
                    join keyword_skills ks
                       on k.id = ks.keyword_id
                       join skills s
                          on ks.skill_id = s.id
           where 
              jk.job_id = 87293
           group by 
              k.id,
              k.name ) PreQuery
      join keyword_skills ks
         on PreQuery.id = ks.keyword_id
         join skills s
             on ks.skill_id = s.id
             AND PreQuery.maxScore = s.Score
   order by 
      PreQuery.Keyword