Slow:
SELECT a.main_id, a.source_id, a.docnum, concat(b.imagepath,a.filename) as image, a.location_id, a.valid, b.rider FROM main a, source b
WHERE a.main_id IN (SELECT main_id
FROM batch_d1
WHERE batch_id=?lnBatch) and a.source_id=b.source_id
Way Fast:
SELECT a.main_id, a.source_id, a.docnum, concat(b.imagepath,a.filename) as image,
a.location_id, a.valid, b.rider
FROM main a, source b, batch_d1 c
WHERE a.main_id=c.main_id and a.source_id=b.source_id and c.batch_id=?lnBatch