>After a break, this has me in the ballpark. Thank you
>
>

>select  ;
>t1.RatingMax	as t1MAX,;
>t2.RatingMax	as t2MAX,;
>t3.RatingMax	as t3MAX,;
>NVL(T1.RatingMax,0) + NVL(T2.RatingMAX,0) + NVL(T3.RatingMAX,0) as SumMAXs, ;
>NVL(T1.yyMMddhh, T2.yyMMddhh)  AS yyT2		,;
>NVL(T1.yyMMddhh, T3.yyMMddhh)  AS yymmddhh	;
>FROM T1	 ;
>FULL JOIN  T2	;
>FULL JOIN  T3	;
>ON T1.yymmddhh = T2.yymmddhh;
>ON T1.yymmddhh = T3.yymmddhh
>

I usually put JOIN conditions right after the JOIN. Also, I think you need double NVL instead, e.g.

>select  ;
>t1.RatingMax	as t1MAX,;
>t2.RatingMax	as t2MAX,;
>t3.RatingMax	as t3MAX,;
>NVL(T1.RatingMax,0) + NVL(T2.RatingMAX,0) + NVL(T3.RatingMAX,0) as SumMAXs, ;
>NVL(NVL(T1.yyMMddhh, T2.yyMMddhh), T3.yymmddhh)  AS yymmddhh	;
>FROM T1	 ;
>FULL JOIN  T2	;
ON T1.yymmddhh = T2.yymmddhh;
>FULL JOIN  T3	;
>ON T1.yymmddhh = T3.yymmddhh