Question

I have two table, defined by this create statement

CREATE TABLE PROJECT (project_name varchar(255), project_budget int, dedicated_project_leader int, dedicated_lead_developer int, dedicated_lead_consultant int, company_id int, project_id int, PRIMARY KEY (project_id));
CREATE TABLE WORKER (worker_name varchar(255), worker_salary int, worker_anual_bonus int, worker_type varchar(255), leader int, company_id int, project_id int, worker_id int, PRIMARY KEY (worker_id));

I’d like to ask for the sum of the budgets of the project than divide it by the number of the workers—)

SELECT (SUM(p.project_budget) / (SELECT count(WORKER.WORKER_NAME) from WORKER)) as AVG_BONUS
  FROM PROJECT p;

Unfortunateley this raise an “ORA–00937:not a single-group group function” exception.

However if i execute this query:

SELECT count(WORKER.WORKER_NAME) from WORKER)

The result will be:

16

And if i divide the summa of budgets with the number instead of the result:

SELECT (SUM(p.project_budget) / 16) as AVG_BONUS
      FROM PROJECT p;

I also got a perfect result e.g.:

294117,647058823

The solution is that i need to group by some id defined at the project table, but don’t think it is logical….

SELECT (SUM(p.project_budget) / (SELECT count(WORKER.WORKER_NAME) from WORKER)) as AVG_BONUS
  FROM PROJECT p
   GROUP BY p.company_id;

It is also working.

Is anyone has a suggestion why can’t i use it? (I have a feeling it is only an sql language specification that there can not exist two group function at a select without group by…)

Answer 1

you have to push each aggregate in this case into its own non-dependant view..eg:

select budget/workers
  from (select (select sum(p.project_budget) from project p) budget,
               (select count(w.worker_name) from worker w) workers
          from dual);