SQL & PL/SQL

Hi everyone,

Looks like i need some help here.. :) dont know what it means but im getting this message
00979. 00000 - "not a GROUP BY expression"
*Cause:
*Action:
Error at Line: 137 Column: 36

this is the function:

function get_path(materialID in number, materialTypeID in number, inTopFolderID in number default null, inMaterialFolderID in number default null, webMode in number default 1)
return varchar2;


and im using it on my query

,(select material_util.get_path(m.material_id, 8, 1021695, min(mf.IP_MATERIALFOLDERID), 1)
from material m, materialfolder mf
where mf.nfx_link = m.MATERIAL_ID
and m.template_id = t.template_id) as Path

looks like min(mf.IP_MATERIALFOLDERID) is having some issues here.. dont know why..

let me know guys..

thanks..

J