The DIGITS function returns a character string representation of the
absolute value of a number.
The argument must be an expression that returns the value of one of the
following built-in numeric data types: SMALLINT, INTEGER, or DECIMAL.
If the argument can be null, the result can be null; if the argument is
null, the result is the null value.
The result of the function is a fixed-length character string representing
the absolute value of the argument without regard to its scale. The result
does not include a sign or a decimal point. Instead, it consists
exclusively of digits, including, if necessary, leading zeros to fill out
the string. The length of the string is:
o 5 if the argument is a small integer
o 10 if the argument is a large integer
o p if the argument is a decimal number with a precision of p