引自 wolfAone, oracle有没有integer类型，这种类型的最大值是多少啊.
Integer是Number类型的子类型：
NUMBER Type
You use the NUMBER datatype to store fixed or floating point numbers
of virtually any size. You can specify precision, which is the total
number of digits, and scale, which determines where rounding occurs.
The syntax follows:
NUMBER[(precision, scale)]
You cannot use constants or variables to specify precision and scale;
you must use integer literals. The maximum precision of a NUMBER value
is 38; the magnitude range is 1.0E-129 .. 9.99E125. If you do not
specify the precision, it defaults to the maximum value supported by
your system.
Scale can range from -84 to 127. For instance, a scale of 2 rounds to
the nearest hundredth (3.456 becomes 3.46). Scale can be negative,
which causes rounding to the left of the decimal point. For example,
a scale of -3 rounds to the nearest thousand (3456 becomes 3000). A
scale of zero rounds to the nearest whole number. If you do not specify
the scale, it defaults to zero.
The NUMBER subtypes below have the same range of values as their base
type. For example, FLOAT is just another name for NUMBER.
DEC
DECIMAL
DOUBLE PRECISION
FLOAT
INTEGER
INT
NUMERIC
REAL
SMALLINT
You can use these subtypes for compatibility or when you want an
identifier more descriptive than NUMBER.