Consider the following database table :
$Emp(\underline{Eid}, Ename, age)$
$Project(\underline{Pid}, Pname,budget)$
$Works for(\underline{Eid Pid})$
Select $Eid$
from $Emp$ $E$
where $age > 30$ and not Exists $(select$ $Pid$
$\text{From project P}$
$\text{where Pname = 'database' and not exist (select Pid}$
$\text{from works W}$
$\text{where W.Eid = E.Eid}$
$\text{and W.Pid = P.Pid))}$
What does the following query return?
More specifically, what does the inner most query do? Would it run only for those eid with age>30 and pid="database" or for all of them?
