Query help

I'm sitting here trying to rewrite query for using with PHP. At first I built it with Access 2010 and there it works like expected. But I need access query in oracle...

It should look for GSPROGRP in table GSDAT and link it to the right name in SDDATEN in table SDAT. The problem is GSPROGRP contains at least 1 up to 4 characters, eg. 05, 16, DR, RGW, but SDKEY in SDDATEN stores it as 0005, 0016, 00DR or 0RGW.

My oracle query doesn't show any result. Can anybody help me with some hints? Maybe sub select or something else? Queries are under my sig.

-- 
Kind regards,

Steffen



Oracle query:
SELECT
	trim(GSPROGRP)                   	AS PrdGrp,
	trim(substr(sddaten, 2, 29))      AS PrdGrpBez
FROM
	GSDAT,
	sddat
where
	GSDAT.GSMANDANT = '00'
	AND (case length(trim(gsprogrp))
         	when 1 then '000' || gsprogrp
                 when 2 then '00' || gsprogrp
                 when 3 then '0' || gsprogrp
                 else gsprogrp
              end) = sddat.sdkey
	AND SDDAT.SDSA = '0196'
ORDER BY
	GSDAT.GSPROGRP;


Access query:
SELECT
	GSDAT.GSPROGRP		AS PrdGrp,
	Trim(Mid(sddaten,2,29))	AS PrdGrpBez
FROM
	GSDAT,
	SDDAT
GROUP BY
	GSDAT.GSPROGRP,
	Trim(Mid(sddaten,2,29)),
	GSDAT.GSMANDANT,
	SDDAT.SDKEY,
	SDDAT.SDSA
HAVING
	(((GSDAT.GSMANDANT)='00')
	AND	((SDDAT.SDKEY)=IIf(Len(Trim(gsprogrp))=1,'000' &
		gsprogrp,IIf(Len(Trim(gsprogrp))=2,'00' &
		gsprogrp,IIf(Len(Trim(gsprogrp))=3,'0 ' &
		gsprogrp,gsprogrp))))
	AND	((SDDAT.SDSA)='0196'))
ORDER BY
	GSDAT.GSPROGRP;