nested joins check

[piedad]

Hallo guys,
I do not really know if either my measured data or my code are not ok. Could you take a look at my Code and give me your feedback, if it is ok to Programm it in this way?
thanks in Advance and Kind regards
Piedad

I have three Databases to join and extract data from:
1st global database with Electric measured data: DB1.Measurements with a Primary key: PRFNR and columns: ID_Long ,Voltage, current,Length, Count,ESD,...
2nd data base with measurement proceduresB1.Tools with a Primary key: PRFNR and columns ID_Long,tools,conditions
3rd Database Linedata: DB2.Data with Primary key ID_Long(just in one Station) and columns ID_short, machinenumber,Date, Status,para1,para2,para3,...
I Need to pick up the Long ID which is only posible to find in the Database DB1.Measurements which corresponds to several Shorts IDs to find in the DB2.Data.
I tried following Code and got some short ID Right results and some result with short ID's belonging to another Databases DB3 and 4.
this is my Code:

Code:

Select Distinct dm.column17 cell, dm.column3 auto_id,dm.column5,dm.column8 Mod_Status,dmZ.column3 BAT,dm7.column4 MOD_VST_ID,
dm7.column8 Mod_Status,dm7.ST_DATUM, dm7.column12 STATUS,DMZ.Date,DMDZ.IR,DMDZ.CAP,DMDZ.UOCV2,DMDZ.DOCV2,
DMDZ.UOCV3,DMDZ.DOCV3,DMDZ.UOCV4,DMDZ.DOCV4,DMDZ.SDR,DMDZ.UBS,DMDZ.DBS,DMDZ.WEIGHT,DMDZ.THICKNESS
 from Data  dm
 
Inner join (Select  PRFNR,column5,column6,column7,column15 from dat_messung  where column2= '1850'  and column5 is not null)dm4 on dm.column19 = dm4.column5
Inner join (Select column15,column5,column6,column7 from dat_messung  where column6 is not null)dm5 on dm4.column6 = dm5.column6 
Inner join (Select column15,column6,column7, PRFNR from dat_messung  where column6 is not null)dm6 on dm5.column7 = dm6.column6  
Inner join (Select DATUM ST_DATUM, column12 ST_Status, PRFNR,column7,column8 from dat_messung  where (column2 = '1330' or column2 = '1360')  
and column7 is not null)dm7 on dm6.column7 = dm7.column7
 
left join (Select Distinct PRFNR PRFNRZ,column3,DATUM Date from DB1.Tools)DMZ ON dm6.colum6 = DMZ.column3
LEFT JOIN(Select * from
     (SELECT Distinct  PRFNR PRFNRX, MNR,X1 FROM ACCU_ZELLE.dat_messungdaten where MNR In(1,2,3,4,5,6,7,8,9,10,11,12,13,14)) 
      PIVOT(Max(X1) For(MNR) IN(1 Voltage1,2 Voltage2,3 Current1,4 Current2,5 Resistane,6 Impedance,7 Width,8 Height,11 Length,12  WEIGHT,13 
      THICKNESS)))DMDZ ON DMZ.PRFNRZ = DMDZ.PRFNRX         
where (dm.DATUM > Sysdate - 60 )