The specified number must be a DOUBLE
PRECISION number.
- If the specified number is NULL, the result of these functions is NULL.
- If the specified number is equal to a mathematical integer, the result
of these functions is the same as the specified number.
- If the specified number is zero (0), the result of these functions is
zero.
- If the specified number is less than zero but greater than -1.0, then
the result of these functions is zero.
The returned value is the smallest (closest to negative infinity)
double floating point value that is greater than or equal to the specified
number. The returned value is equal to a mathematical integer. The data type
of the returned value is a DOUBLE PRECISION number.