Interesting though esoteric problem of the form 'select a * b from dual'

Question

Hi,
Warning: The question is of very little practical significance.
(There, I warned you!!)
Database version: 10.2.0.4.0
If I try to execute the following
select 9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999 * 999999999999999999999999999999999999999999
from dualI get a 'ORA-01426: numeric overflow' error, which is fine.
But if I try to execute the following(note the decimal point)
select 3.14285712285715111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111 * 7
  from dualI get a 'ORA-00923: FROM keyword not found where expected' error.
Interestingly, if I remove any one digit from the first number(hence reducing its length by 1), the query works fine. Removing the spaces on either side of '*' still results in a 'ORA-00923: FROM keyword not found where expected' error though.
Can anyone explain why?
Regards,
Sujoy

Answer 1

Hi, Sujoy,
There seems to be a limit of 255 characters (including decimal point) in a number literal. It doesn't seem to matter how m,any digits are before the decimal point and how many are after it. If you don't raise siome other error (such as "'ORA-01426: numeric overflow' error") first, then using a liteal with more than 255 characters will raise "'ORA-00923: FROM keyword not found where expected".
Multiplying by 7 in your example doesn't matter; the compiler never gets that far, because the error occurs in the compilation.
A sign doesn't matter, either, because signs are not part of the literal; they are operators applied to the value after the literal is evaluated. This is also evident because you can put withespace between the sign and the literal.