Question

I’m trying to select all Projects which have Employees who are AtWork.

Projects:
ProjName    |    EmpOnProj
--------------------------
Alpha       |    1, 2, 3
Beta        |    1, 3

Employees:
EmpID       |   EmpName    |   AtWork
-------------------------------------
1           |   John       |   TRUE
2           |   Mark       |   FALSE
3           |   Mary       |   TRUE

I need to output all projects which could currently be worked on; ie, I need to show Beta because the employees working on Beta are at work.

Currently I cannot say “ALL EMPLOYEES MUST BE AT WORK” only the following:

SELECT ProjName FROM Projects INNER JOIN 
Employees ON EmpOnProj.Value = EmpID
WHERE AtWork = true
GROUP BY ProjName

which returns both, as it sees one correct employee and displays the project.

Answer 1

I think I solved this one. Basically I’m saying ‘show all projects except those where somebody is NOT at work’

http://sqlfiddle.com/#!3/36c48/2

SELECT DISTINCT
  p_global.ProjName 

FROM
  Projects AS p_global

WHERE
  p_global.ProjName NOT IN
    (SELECT DISTINCT
      p1.ProjName

    FROM 
      Projects p1 INNER JOIN Employees AS e ON p1.EmpOnProj = e.EmpID 

    WHERE
      e.AtWork = 0)

There may be a simpler solution but this works (or it looks like it anyway) 🙂

Edit: Modified to remove GROUP BYs as suggested in comments.