select I.CLV_ART, CAMPOSTRU1, I.CAMPOSTRU3, CAMPOINTU,CAMPODBL4,CAMPODBL8,
(select sum(MI.CANT) suma from tablaInt MI
where MI.clv_art = I.clv_art
AND MI.TIPO_MOV IN (51)
and extract(month from FECHA_DOCU)=4
and extract(year from FECHA_DOCU)=2008) as venta1 <--//creo que falta esto
from tabla1 I
where I.STATUS='A'
and I.CAMPOSTRU3='HILO LATEX'
and I.CAMPOSTRU2='LATEX 40BL40EX'
GROUP BY CLV_ART, CAMPOSTRU1, CAMPOINTU,CAMPODBL4,CAMPODBL8,I.CAMPOSTRU3