c# - add column to existing query with GROUP BY -

i have got little issue, i'm trying put column klisluz.cena existing query giving me errors that: column klisluz.cena in command select isnt correct, because not in group by, when insert in group throws same error. should put ?

thanks in advance. query:

 string squery = string.format("select zajsluz.akce,zajsluz.text,klisluz.pocet,klisluz.cena,klisluz.subkey,zajsluz.id zajsluz left join klisluz on zajsluz.id=klisluz.idzajsluz zajsluz.akce= '{0}' , isnull(klisluz.subkey, '" + vyberradek + "') = '" + vyberradek + "' group klisluz.subkey,zajsluz.akce,zajsluz.text,klisluz.pocet,zajsluz.id", szakce); 

if column "cena" numeric price value, perform aggregate function on it.

you try use max(klisluz.cena) maximum value, or sum(..) sum other 1 apply column type.

http://msdn.microsoft.com/en-us/library/ms173454.aspx