I tried this formula: =concatenate(query('Scheda Intervento'!C2:K14;select SUM (K) where (F>= date '2013-01-01' and F <= date '2013-01-31' and C = ' & A2 &');0))The result is right but it gives me:sum  35 but I want to have 35 
Problem QUERY function in Google Spreadsheets formula
google spreadsheets
Use the following formula:=INDEX(query('Scheda Intervento'!C2:K13;select sum (K)  where (F >= date '2013-01-01' and F <= date '2013-01-31'  and C = ' & A2 &'));2;1)After that you can perform the CONCAT handling.