Improve SQL Performance

Hello,
I have a query that I'd like to improve the performance on. The engine is Pervasive PSQL8

Select J.Custno,J.ShipAddress1,J.Jobnum,JL.Linenum,JL.PartNumber,JL.JobSerialNumber,JL.Item,JL.FilterSize,JL.Description,JL.Quantity,J.ReceiveDate,J.ProjectedShipDate,W.CheckInDate,W.CheckOutDate from Jobs J, Prodv2 P, ItemBOM I,{oj JobLinesv2 JL left outer join WIP W on JL.Jobnum=W.Jobnum and JL.JobSerialNumber=W.JobSerialNumber}
where J.InvoiceDate = '1899-12-31'
and J.Canceled=0
and JL.Jobnum=J.Jobnum
and JL.Item<>''
and JL.PartNumber<>''
and SubString(I.LinePartNumber,1,3) IN ('012','013','200','201','201')
and SubString(JL.PartNumber,1,3)=SubString(I.PartNumber,1,3)
and SubString(JL.PartNumber,11,2)=SubString(I.PartNumber,11,2)
and P.Item=JL.Item
and P.Suppno='SMI01'
and P.IsStock=0
order by JL.Jobnum,JL.Linenum

Thanks for any help.
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