Question

I have been reading Beginners guide for oracle DB. The definition for precision and scale are quite confusing.
Book says:

number(6,3) 

Oracle allows for 2 not 6 significant digitalis.

my problem is, 6 means precision. which means number of significant digits. so it should accept 6 significant digits. why does the book says it is 2 significant digits

The book i am referring to is Oracle Database 11g A Beginner’s Guide by McGraw Hill Professional, Dec 18, 2008, page number 12

Answer 1

Check out the online Oracle doc:

p is the precision, or the maximum 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.