Need A Solution ... Urgently

These two queries when executed seperately give results in under 10 secs

A union between these two does not give results even after 20 minutes ...

Any idea why this is happening


SELECT
T001W.NAME1,
t25a5.bezek SKU,
QTY = SUM(CASE MSEG.BWART
WHEN '101' THEN MSEG.ERFMG
WHEN '102' THEN (-1)*MSEG.ERFMG END),
YPLNT.VKGRP
FROM MARA ,MSEG, MKPF,YPLNT,T001W,t25a5
WHERE
MSEG.MANDT = MKPF.MANDT
AND MKPF.MANDT = MARA.MANDT
and mkpf.mandt =yplnt.mandt
and mkpf.mandt = t25a5.mandt
AND MKPF.MBLNR = MSEG.MBLNR
AND MARA.MATNR = MSEG.MATNR
AND YPLNT.PPLNT= MSEG.WERKS
AND MSEG.WERKS = T001W.WERKS
and t25a5.ww004 = SUBSTRING(MARA.PRDHA, 10, 3)
AND MARA.PRDHA <> ''
AND MKPF.VGART IN ('WR','WF')
AND MKPF.MJAHR=YEAR(@BUDAT1)
AND MSEG.AUFNR IS NOT NULL
AND MSEG.BWART IN ('101','102')
GROUP BY t25a5.bezek,T001W.NAME1,YPLNT.VKGRP

SELECT
T001W.NAME1,
t25a2.bezek SKU,
QTY = SUM(CASE MSEG.BWART
WHEN '101' THEN MSEG.ERFMG
WHEN '102' THEN (-1)*MSEG.ERFMG END),
YPLNT.VKGRP

FROM MARA ,MSEG, MKPF,YPLNT,T001W,t25a2
WHERE
MSEG.MANDT = MKPF.MANDT
AND MKPF.MANDT = MARA.MANDT
and mkpf.mandt =yplnt.mandt
and mkpf.mandt = t25a2.mandt
AND MKPF.MBLNR = MSEG.MBLNR
AND MARA.MATNR = MSEG.MATNR
AND YPLNT.PPLNT=MSEG.WERKS
AND MSEG.WERKS = T001W.WERKS
and t25a2.ww001 = SUBSTRING(MARA.PRDHA, 1, 3)
AND MARA.PRDHA <> ''
AND MKPF.MJAHR=YEAR(@BUDAT1)
AND MKPF.VGART IN ('WR','WF')
AND MSEG.AUFNR IS NOT NULL
AND MSEG.BWART IN ('101','102')
GROUP BY t25a2.bezek,T001W.NAME1,YPLNT.VKGRP