mysql - SQL SELECT Query -


suppose have sql table "company" 3 columns: "department_id", "employee", "job". this:

departament_id | employee | job -------------------------------------- 1              | mark     | president 1              | robert   | marketing manager 1              | rose     | administration assitant 2              | anna     | programmer 2              | michael  | programmer 2              | celia    | sales manager 3              | jhon     | sales manager 3              | donna    | programmer 3              | david    | marketing manager

i write query returns departments id @ least 50% of jobs same.

result need in example just:

departament_id | -------------------------------------- 2              |

how write sql query? think tried kind of stuff dont :(.

this bit tricky. need compare total number of people on job in department total number. so, 1 method uses 2 aggregations:

select department_id (select department_id, count(*) numemp       t       group department_id      ) d join      (select department_id, max(numemp) numemp       (select department_id, job, count(*) numemp             t             group department_id, job            ) d      group department_id     ) dj     on d.numemp <= 2 * dj.numemp;

you might duplicates if have 1 department split between 2 jobs. in case, use select distinct.


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