Returning errors as with Group By

Question

It seems as if once I use Group By in my query I begin returning errors in my where clause.

SELect Rtrim(riders.firstName)||' '||rtrim(riders.lastname) AS Rider_Name, teams.teamname, Rtrim(agents.firstName)||' '||rtrim(agents.lastname) AS Agent_Name
FROM Riders, teams, agents, participation, races
Where teams.teamID = riders.teamID
and agents.agentID = riders.agentID
and participation.riderID = riders.riderid
and races.raceid = participation.raceid
and races.RaceDate Between '01-Apr-2008' and '30-Apr-2008'

That returns the results I need, but I need to eliminate any duplicates so i've done

Group BY Rtrim(riders.firstName)||' '||rtrim(riders.lastname)

and

Group BY participation.riderID

and

Group By rider.riderID

and those were my best guesses. here is the full code.

SQL> SELect Rtrim(riders.firstName)||' '||rtrim(riders.lastname) AS Rider_Name,
teams.teamname, Rtrim(agents.firstName)||' '||rtrim(agents.lastname) AS Agent_Na
me
  2  FROM Riders, teams, agents, participation, races
  3  Where teams.teamID = riders.teamID
  4  and agents.agentID = riders.agentID
  5  and participation.riderID = riders.riderid
  6  and races.raceid = participation.raceid
  7  and races.RaceDate Between '01-Apr-2008' and '30-Apr-2008'
  8  Group BY participation.riderid
  9  ;
SELect Rtrim(riders.firstName)||' '||rtrim(riders.lastname) AS Rider_Name, teams
.teamname, Rtrim(agents.firstName)||' '||rtrim(agents.lastname) AS Agent_Name
             *
ERROR at line 1:
ORA-00979: not a GROUP BY expression

Answer 1

If you want to eliminate exact duplicate rows, you can just use select distinct:

SELect DISTINCT Rtrim(riders.firstName)||' '||rtrim(riders.lastname) AS Rider_Name,
       teams.teamname, Rtrim(agents.firstName)||' '||rtrim(agents.lastname) AS Agent_Name

Then don't use the group by.

Answer 2

I'd recommend using Group By rider.riderID

you just need to add rider.riderID into the fields list

FWIW group by is faster than distinct