Dynamic date data retreival

Here is your actual SQL statement. You'll need to head over to a SQL forum to get someone to help. Someone here might be able to assist, but a SQL forum as a bunch of people that can assist.

SELECT Leg."legnr", 
       Leg."salesorder", 
       Row_number() 
         OVER ( 
           partition BY Leg.salesorder 
           ORDER BY legnr)                               AS SalesOrderLine, 
       Leg."legstatus", 
       Leg."planned", 
       Leg."salesinvoice", 
       Isnull(Leg.ediprovider, '987654321')              AS EDIProvider, 
       Leg."distance", 
       Leg."orderleg", 
       Leg."plangroup"                                   AS 'FK PlanGroup', 
       Leg."findate", 
       Leg."totalamount", 
       Leg."costs", 
       Leg."cmrreceived", 
       Leg.[emailsalesinvoice], 
       Leg.[reference], 
       Leg."creationuser", 
       Leg.[cargo], 
       --Leg.BeginActivity, 
       --leg.EndActivity, 
       Isnull(B."address", ( b.activitynr + 900000000 )) AS BeginAddress, 
       B."date"                                          AS BeginDate, 
       B."datetill"                                      AS BeginDateTill, 
       B."time"                                          AS BeginTime, 
       B."timetill"                                      AS BeginTimeTill, 
       B."resourcecombination"                           AS 
       BeginResourceCombination, 
       B."tripid"                                        AS BeginTripID, 
       B."startdate"                                     AS BeginStartDate, 
       B."starttime"                                     AS BeginStartTime, 
       B."enddate"                                       AS BeginEndDate, 
       B."endtime"                                       AS BeginEndTime, 
       B."activityduration"                              AS 
       BeginActivityDuration, 
       Isnull(E."address", ( e.activitynr + 800000000 )) AS EndAddress, 
       E."date"                                          AS EndDate, 
       E."datetill"                                      AS EndDateTill, 
       E."time"                                          AS EndTime, 
       E."timetill"                                      AS EndTimeTill, 
       E."resourcecombination"                           AS 
       EndResourceCombination, 
       E."tripid"                                        AS EndTripID, 
       E."startdate"                                     AS EndStartDate, 
       E."starttime"                                     AS EndStartTime, 
       E."enddate"                                       AS EndEndDate, 
       E."endtime"                                       AS EndEndTime, 
       E."activityduration"                              AS EndActivityDuration, 
       leg.creationdate, 
       Sum(Cargo."weight")                               AS Weight, 
       Sum(Cargo."loadingmeter")                         AS LoadingMeter, 
       Sum(Cargo."palletplaces")                         AS PalletPlaces, 
       CASE 
         WHEN legnr IN (SELECT DISTINCT [leg] AS [pl_orders] 
                        FROM   so_cargo 
                        WHERE  unit = 78) THEN 'pl' 
         ELSE NULL 
       END                                               AS [pl order] 
-- unit 78 = pl 
FROM   so_leg AS Leg 
       LEFT JOIN so_activity AS B 
              ON leg.beginactivity = B.activitynr 
       LEFT JOIN so_activity AS E 
              ON leg.endactivity = E.activitynr 
       LEFT JOIN so_cargo AS cargo 
              ON leg.[legnr] = cargo.leg 
WHERE  findate >= Dateadd(year, -3, CONVERT (DATE, Dateadd(year, Datediff(year, 
                                                                 0, 
                                                                 Getdate()) + 1, 
                                                                     0))) 
GROUP  BY Leg."legnr", 
          Leg."salesorder", 
          Leg."legtype", 
          Leg."legstatus", 
          Leg."planned", 
          Leg."salesinvoice", 
          Leg.ediprovider, 
          Leg."distance", 
          Leg."orderleg", 
          Leg."plangroup", 
          Leg."findate", 
          Leg."totalamount", 
          Leg."costs", 
          Leg."cmrreceived", 
          Leg.[emailsalesinvoice], 
          Leg.[reference], 
          Leg."creationuser", 
          Leg.cargo, 
          --Leg.BeginActivity, 
          --Leg.EndActivity, 
          leg.creationdate, 
          B.activitynr, 
          B."activitykind", 
          B."address", 
          B."date", 
          B."datetill", 
          B."time", 
          B."timetill", 
          B."resourcecombination", 
          B."tripid", 
          B."startdate", 
          B."starttime", 
          B."enddate", 
          B."endtime", 
          B."activityduration", 
          E."activitykind", 
          E."address", 
          E."date", 
          E."datetill", 
          E."time", 
          E."timetill", 
          E."resourcecombination", 
          E."tripid", 
          E."startdate", 
          E."starttime", 
          E."enddate", 
          E."endtime", 
          E."activityduration", 
          E.activitynr 

Or, post some sample data and tell us what you are trying to do and we can start from scratch with Power Query. 

You should rarely/never use that advanced SQL dialog box. Either create a View on the SQL server, or do it in Power Query. Doing it via an advanced SQL statement can cause permissions issue and prevents simple edits. I could adjust an M statement to only get the last 4 days of info in 2-3 lines that would fold back to the server. Nothing after an advanced SQL statement entry will allow folding.