Ah, OK. This was my first idea to solve the problem. But being an "old style" .net programmer I thought there was a more effective built in way to do it. Stream and loop, simple enough... I'll skip the regex and find the position fo "y = " and "/>" and grab the string between those positions.

WOW! I've tried different indexes on the large table but I never got i right. Now this baby: SELECT Intervallvarden.storhet, Intervallvarden.id_intervallvarde, Intervallvarden.varde, Intervallvarden.tid, Intervallvarden.kanal_nr, MatpunktInstrument.instrumenttyp, MatpunktInstrument.instrumentnummer FROM MatpunktInstrumentParameter INNER JOIN MatpunktInstrument ON MatpunktInstrumentParameter.id_matpunkt_instrument_parameter = MatpunktInstrument.id_matpunkt_instrument_parameter INNER JOIN Intervallvarden ON Intervallvarden.instrument_typ = MatpunktInstrument.instrumenttyp AND Intervallvarden.instrument_nr = MatpunktInstrument.instrumentnummer AND Intervallvarden.tid > MatpunktInstrumentParameter.tid_upp WHERE (MatpunktInstrumentParameter.id_matpunkt = 2575) AND (Intervallvarden.tid > '2007-10-01 00:00') AND (Intervallvarden.tid < '2007-11-30 23:00') ORDER BY intervallvarden.tid Runs in two seconds! Table "Intervallvarden" being the 30 milion rows table. Thanks allot!