i know basic difference between them ,i wanted to know
if i do not specify precision and scale and define the datatype as number what are the default values for precision and scale assigned?
create table a(id number);
create table b(id number(3));
both above queries creates a table with column and number datatype but what is the difference from 1)performance point of view 2)How it is handled internally by database 3)Is there any advantage of specifying number as datatype over number(3)
Answer from Oracle perspective...
NUMBER Datatype
The NUMBER datatype stores zero as well as positive and negative fixed numbers with absolute values from 1.0 x 10-130 to (but not including) 1.0 x 10126. If you specify an arithmetic expression whose value has an absolute value greater than or equal to 1.0 x 10126, then Oracle returns an error. Each NUMBER value requires from 1 to 22 bytes.
Specify a fixed-point number using the following form:
NUMBER(p,s)
where:
p is the precision, or the total number of significant decimal digits, where the most significant digit is the left-most nonzero digit, and the least significant digit is the right-most known digit. Oracle guarantees the portability of numbers with precision of up to 20 base-100 digits, which is equivalent to 39 or 40 decimal digits depending on the position of the decimal point.
s is the scale, or the number of digits from the decimal point to the least significant digit. The scale can range from -84 to 127.
Positive scale is the number of significant digits to the right of the decimal point to and including the least significant digit.
Negative scale is the number of significant digits to the left of the decimal point, to but not including the least significant digit. For negative scale the least significant digit is on the left side of the decimal point, because the actual data is rounded to the specified number of places to the left of the decimal point. For example, a specification of (10,-2) means to round to hundreds.
Scale can be greater than precision, most commonly when e notation is used. When scale is greater than precision, the precision specifies the maximum number of significant digits to the right of the decimal point. For example, a column defined as NUMBER(4,5) requires a zero for the first digit after the decimal point and rounds all values past the fifth digit after the decimal point.
It is good practice to specify the scale and precision of a fixed-point number column for extra integrity checking on input. Specifying scale and precision does not force all values to a fixed length. If a value exceeds the precision, then Oracle returns an error. If a value exceeds the scale, then Oracle rounds it.
Specify an integer using the following form:
NUMBER(p)
This represents a fixed-point number with precision p and scale 0 and is equivalent to NUMBER(p,0).
Specify a floating-point number using the following form:
NUMBER
The absence of precision and scale designators specifies the maximum range and precision for an Oracle number.
And
NUMBER[(precision [, scale]])
Number having precision p and scale s. The precision p can range from 1 to 38. The scale s can range from -84 to 127
