SELECT T_Production.Produktion_ID, T_Production.Model, T_Test.Test_SerieNr, T_Assembly1.Montering_SerieNr
FROM (T_Production LEFT JOIN T_Assembly1 ON T_Production.Produktion_ID = T_Assembly1.Prod_ID) LEFT JOIN T_Test ON T_Production.Produktion_ID = T_Test.Prod_ID;