>>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
>

Thanks. I couldn't figure out why my results were so off, but with the nested NVL's, it's working fine. I changed the date variable to YYMM since that's what it is displaying, based on the output of the previous queries for each table.

SET SAFETY off
select  				;
t4.RatingMax	as t4MAX	,;
t5.RatingMax	as t5MAX	,;
t7.RatingMax	as t7MAX	,;
t9.RatingMax	as t9MAX	,;
t11.RatingMax	as t11MAX	,;
t12.RatingMax	as t12MAX	,;
t1.RatingMax	as t1MAX	,;
t2.RatingMax	as t2MAX	,;
NVL(T4.RatingMax,0) +;
NVL(T5.RatingMAX,0) +;
NVL(T7.RatingMAX,0) +;
NVL(T9.RatingMAX,0) +;
NVL(T11.RatingMAX,0) +;
NVL(T12.RatingMAX,0) +;
NVL(T1.RatingMAX,0) +;
NVL(T2.RatingMAX,0) ;
as SumMAXs	, ;
NVL(;	&&7
NVL(;	&&6
NVL(;	&&5
NVL(;	&&4
NVL(;	&&3
NVL(;	&&2
NVL(;	&&1
T4.yymm		,; 	
T5.yymm)	,;	&&1
T7.yymm)	,;	&&2
T9.yymm)  	,;	&&3
T11.yymm)  	,;	&&4
T12.yymm)  	,;	&&5
T1.yymm)  	,;	&&6
T2.yymm)  	;	&&7
AS yymm	;
FROM T4	 ;
FULL JOIN  T5  ON T4.yymm = T5.yymm;
FULL JOIN  T7  ON T4.yymm = T7.yymm;
FULL JOIN  T9  ON T4.yymm = T9.yymm;
FULL JOIN  T11 ON T4.yymm = T11.yymm;
FULL JOIN  T12 ON T4.yymm = T12.yymm;
FULL JOIN  T1  ON T4.yymm = T1.yymm;
FULL JOIN  T2  ON T4.yymm = T2.yymm;
order BY t4.yymm;
into table gg
brow width 10

The output is like this now, and is something that I can easily automate into excel: I started with T4 because it has more dates,
and T1 - T2 were missing some. This is a big change from relying on set relation. Thanks again!

T4max   T5max   T7max ...   T1max   SumMAxs   YYmm
1.1       2.2   1.2   ...     NULL        4.5           201201
1.0       2.0   1.0   ...     NULL        4.0           201202