遇到mysql設計的是6位float數經緯度，賦值的時候，明明是準去的資料insert進去，但是卻發現，資料自動變了，精度明顯丟失。檢視官方文件才發現

https://dev.mysql.com/doc/refman/5.7/en/problems-with-float.html

確實是有問題，但是mysql已經有另外的方式解決了這個問題，那就是decimal

Floating-point numbers sometimes cause confusion because they are approximate and not stored as exact values. A floating-point value as written in an SQL statement may not be the same as the value represented internally. Attempts to treat floating-point values as exact in comparisons may lead to problems. They are also subject to platform or implementation dependencies. The 

大體就是這個意思