关于Postgresql数据类型numeric的 precision和scale
参考自：
https://www.postgresql.org/docs/10/static/datatype-numeric.html#DATATYPE-NUMERIC-TABLE
scale是小数点右边小数部分 小数的位数，
原文链接：https://www.f2er.com/postgresql/193174.html参考自：
https://www.postgresql.org/docs/10/static/datatype-numeric.html#DATATYPE-NUMERIC-TABLE
We use the following terms below: The scale of a numeric is the count of decimal digits in the fractional part,to the right of the decimal point. The precision of a numeric is the total count of significant digits in the whole number,that is,the number of digits to both sides of the decimal point.
scale是小数点右边小数部分 小数的位数，
precision是小数点两边所有数字中，有效数字的位数。
the number 23.5141 has a precision of 6 and a scale of 4.
Integers can be considered to have a scale of zero.