En SQLPlus podemos crear una vista que incluya rownum para ver exactamente qué tipo de datos usa Oracle:
TEST>create view v_test as select rownum rn, dummy from dual;
View created.
TEST>desc v_test
Name Null? Type
-------- -------- -------------
RN NUMBER
DUMMY VARCHAR2(1)
Entonces, para Oracle, esta pseudocolumna es un Número. Que basado en este enlace ( http:/ /download.oracle.com/docs/cd/B28359_01/server.111/b28318/datatype.htm#i16209 ) puede contener:
The following numbers can be stored in a NUMBER column:
-Positive numbers in the range 1 x 10^-130 to 9.99...9 x 10^125 with up to 38 significant digits
-Negative numbers from -1 x 10^-130 to 9.99...99 x 10^125 with up to 38 significant digits
-Zero
-Positive and negative infinity (generated only by importing from an Oracle Database, Version 5)
