K / 3 Cloud documents related queries

Sales Delivery pushed down sales return orders, learn how their relationship? 
T_SAL_OUTSTOCKENTRY is Sales Delivery entry 
T_SAL_RETURNSTOCKENTRY sales return is a single entry 
T_SAL_RETURNSTOCKENTRY_LK is sales returns alone, according to the associated configuration table (table)

FSBILLID a single source ID, the FSID is the ID entry source

select T_SAL_OUTSTOCKENTRY.FREALQTY 
,isnull(T_SAL_RETURNSTOCKENTRY.FREALQTY,0)
 from T_SAL_OUTSTOCKENTRY  
    left join T_SAL_RETURNSTOCKENTRY_LK
      on T_SAL_OUTSTOCKENTRY.FID  = T_SAL_RETURNSTOCKENTRY_LK.FSBILLID
      and T_SAL_OUTSTOCKENTRY.FENTRYID = T_SAL_RETURNSTOCKENTRY_LK.FSID
    left join T_SAL_RETURNSTOCKENTRY
      on T_SAL_RETURNSTOCKENTRY.FENTRYID = T_SAL_RETURNSTOCKENTRY_LK.FENTRYID
    where  T_SAL_OUTSTOCKENTRY.FID = 173384