Creating joins correctly

Question

I have been asked to create a sales opportunity report which returns a selection of fields from OOPR, OPR1, OPR3, OPR4 and OCPR.  For starters I have the following:
SELECT DISTINCT T0.OpprId, T0.CardCode, T0.CardName, T0.OpenDate, T0.PredDate, T2.ClosePrcnt, T4.ThreatLevl, T4.Memo, T4.Won, T1.U_Country,  T1.U_Source, T3.Descript, T5.Name
FROM OOPR  T0 INNER JOIN OCPR  T1 ON T0.CprCode = T1.CntctCode INNER JOIN OPR1  T2 ON T0.OpprId = T2.OpprId INNER JOIN OOST  T3 ON T0.StepLast = T3.Num, OPR3  T4 INNER JOIN OCMT  T5 ON T4.CompetId = T5.CompetId
This does not include OPR4 yet.  My first problem is that it returns multiple lines for each opportunity based around permutations of stage and competitor.  I have tried INNER, LEFT and RIGHT joins but have the same problem.  I'm obviously missing something fairly fundamental.  If I then try to JOIN in OPR4 I lock up the system until it brings back 105,000 result!  We currently have a total of 360 opportunities!
Thanks for your time

Answer 1

I have now seen one area which would cause this.  Step_Id shows the stages of the opportunity there are therefore usually more than one stage.  This query returns all stages.  Any thoughts on how we return just the last one.