DECIMAL Data Type

In MySQL, DECIMAL(M,D) and NUMERIC(M,D) are the same, and both have a precision of exactly M digits.

Leftover Digits    Number of Bytes
0   　　　　　　　　　　0
1–2   　　　　　　　　 1
3–4    　　　　　　　　2
5–6    　　　　　　　　3
7–9   　　　　　　　　 4

 For example,

a DECIMAL(18,9) column has nine digits on either side of the decimal point, so the integer part and the fractional part each require 4 bytes.

A DECIMAL(20,6) column has fourteen integer digits and six fractional digits.

The integer digits require four bytes for nine of the digits and 3 bytes for the remaining five digits.

The six fractional digits require 3 bytes.

转载于:https://www.cnblogs.com/zengkefu/p/5618994.html