ORA-00945: specified clustered column does not exist

here’s the code with the cluster included, the table never gets created and oracle documentation is ass

create cluster c123 (a integer)
size 512;
/

drop table t123;
/

create table t123
cluster c123 (b)
as SELECT t1.col1 FROM T1, T2, T3
WHERE T1.col1=T3.col11 AND
T2.col1=T3.col12 AND T1.col2=1;
/

it needs to create the table, instead i keep getting

...
Error report -
ORA-00945: specified clustered column does not exist
00945. 00000 -  "specified clustered column does not exist"
*Cause:    
*Action:

Answer

You could add alias:

create table t123
cluster c123 (b)
as 
SELECT t1.col1 AS b
FROM T1
JOIN T2 ON T1.col1=T2.col11
JOIN T3 ON T2.col1=T3.col12
WHERE T1.col2=1;