Essaye ca:
Select a.ID, a.Emetteur, a.Montant, a.Date_Encaissement, a.Encaisse
From paiments a
Join paiements b on b.Emetteur = a.Emetteur And b.Date_Encaissement like '%2010%' And b.Encaisse = '1' and b.Mode = 'CHQ'
Where a.Mode = 'CHQ'
And a.Date_Encaissement like '%2011%'
And a.Encaisse = '0'