Вам просто нужны substr и row_number ()
Select
Substr(email,INSTR(email,'@')+1, length(email)) as "Domain",
Substr(email,1,INSTR(email,'@')-1) as
"User", row_number() over
(partition by
Substr(email,INSTR(email,'@')+1,length(email)) order
by Substr(email,INSTR(email,'@')+1, length(email)) )
from table;
![enter image description here](https://i.stack.imgur.com/OnIUS.png)