update row always has results but still doesn't work

I have this script in my database, but it always gives 2054 rows back and if I actually DO change something it doesn't even notice...what am I doing wrong in hereUPDATE aSET a.[omschrijving] = SP.[omschrijving] ,a.[verkoopprijs] = SP.[verkoopprijs] ,a.[gewijzigd] = getDate()FROM [artikelen] aLEFT OUTER JOIN [Hofstede].[dbo].[sparepartsupdate] SP ON a.PartNrFabrikant = sp.PartNrFabrikantWHERE ((A.omschrijving != SP.[omschrijving]) OR (A.[verkoopprijs] != SP.[verkoopprijs]))