SELECT
'REP' AS Tbl,
Rep.PR AS PR,
Rep.PO AS PO,
Rep.SO AS SO,
REP. YA AS YA
FROM
GAD_RAS AS Rep
UNION
-----SPR DATA
SELECT
'SPR' AS Tbl,
Ord.SAP_PR AS PR,
Ord. SAP_PO AS PO,
Ord.SAP_SO AS SO,
Ord.SAP_YA AS YA
FROM
SAP_TRS AS Ord
/*ORDER BY ...*/
You should also change the UNION to UNION ALL here. That may require adding DISTINCT to each query - if the individual queries are returning duplicates.
UNION will add a sort to remove duplicates - but each set would not have duplicates because of the 'type' column.