Question

Assume 2 tables:

TABLE: team
-----------
| team_id |
===========
| 1       |
-----------
| 2       |
-----------

TABLE: team_member
-------------------------------------------
| team_member_id | team_id | age | gender |
===========================================
| 1              | 1       | 20  | Male   |
-------------------------------------------
| 1              | 2       | 25  | Male   |
-------------------------------------------
| 1              | 2       | 23  | Female |
-------------------------------------------

How do I search for things like this:

1. List of all teams that are only male, between ages of 18 and 25.
2. List of all teams that are male and female, where either gender is between ages of 18 and 25.
3. Etc.

I’m basically looking for general strategies on how to apply certain filters (e.g. age) across all the children records of team. Suggestions?

Answer 1

team, team_member

You can’t just apply a simple WHERE clause if you are checking for only an all male or all female team… it needs to be compared against the full set of team members. Try

select 
      tm.team_id,
      sum( if( tm.gender = 'Male' AND tm.age between 18 and 25, 1, 0 )) as MaleInRange,
      count(*) AllTeamMembers
  from
      team_member tm
  group by
      tm.Team_ID
  having
      MaleInRange = AllTeamMembers

Similarly, to ensure you have BOTH male AND female…

select 
      tm.team_id,
      sum( if( tm.age between 18 and 25, 1, 0 )) as AgeInRange,
      sum( if( tm.gender = 'Male', 1, 0 )) as MaleCnt,
      sum( if( tm.gender = 'Female', 1, 0 )) as FemaleCnt,
      count(*) AllTeamMembers
  from
      team_member tm
  group by
      tm.Team_ID
  having
         AgeInRange = AllTeamMembers
     AND MaleCnt > 0
     AND FemaleCnt > 0