Query breaks whenever I add MAX() functions or grouping statements - c++

Question

I have some tables laid out like so:
Airplane
(airplaneID number(2) primary key, airplaneName char(20), cruisingRange number(5));
Flights
(airplaneID number (2), flightNo number(4) primary key,
fromAirport char(20), toAirport char(20), distance number(4), depart timestamp,
arrives timestamp, foreign key (airplaneID) references Airplane);
Employees
(employeeID number(10) primary key, employeeName char(18), salary number(7));
Certified
(employeeID number(10), airplaneID number(2),
foreign key (airplaneID) references Airplane,
foreign key (employeeID) references Employees );
And I need to write a query to get the following information:
For each pilot who is certified for at least 4 airplanes, find the
employeeName and the maximum cruisingRange of the airplanes for which
that pilot is certified.
The query I have written is this:
SELECT Employees.employeeName, MAX(Airplane.cruisingRange)
FROM Employees
JOIN Certified ON Employees.employeeID = Certified.employeeID
JOIN Airplane ON Airplane.airplaneID = Certified.airplaneID
GROUP BY Employees.employeeName
HAVING COUNT(*) > 3
Lastly, this is the function that executes and reads in the query information:
void prepareAndExecuteIt() {
// Prepare the query
//sqlQueryToRun.len = strlen((char *) sqlQueryToRun.arr);
exec sql PREPARE dbVariableToHoldQuery FROM :sqlQueryToRun;
/* The declare statement, below, associates a cursor with a
* PREPAREd statement.
* The cursor name, like the statement
* name, does not appear in the Declare Section.
* A single cursor name can not be declared more than once.
*/
exec sql DECLARE cursorToHoldResultTuples cursor FOR dbVariableToHoldQuery;
exec sql OPEN cursorToHoldResultTuples;
int i = 0;
exec sql WHENEVER NOT FOUND DO break;
while(1){
exec sql FETCH cursorToHoldResultTuples INTO empName, cruiseRange;
printf("%s\t", empName);
printf("%s\n", cruiseRange);
i++;
// This is temporary while I debug so it doesn't just loop on forever when the query breaks.
if (i > 500){
printf("Entered break statement\n");
break;
}
}
exec sql CLOSE cursorToHoldResultTuples;
}
The query works until I add the MAX(), GROUP BY, and HAVING statements. Then it just reads in nothing infinitely. I don't know if this is an issue with the way I've written my query or if it's an issue with the C++ code that executes it. I'm using the ProC interface to access an Oracle database. Any ideas as to what's going wrong?

Answer 1

You can't mix implicit and explicit joins. I suggest
SELECT Employees.employeeName, MAX(Airplane.cruisingRange)
FROM Employees
JOIN Certified ON Employees.employeeID = Certified.employeeID
JOIN Airplane ON Airplane.airplaneID = Certified.airplaneID
GROUP BY Employees.employeeName
HAVING COUNT(*) > 3
which works fine.
db<>fiddle here