title: how to store bitcoin and other currencies in mysql database
body: <p>I try to make payment system. Customers can make purchases with bitcoin or other curriencies like (USD,EUR) i have a decimal amount column with (16,8), for bitcoin amounts it works normally, but when i try to put usd value for example 100 usd , it becomes 100.00000000 , my question is should store amount like this ? use same decimal column for bitcoin and other currencies? is it bad for performance when counting all records? or should i have multiple column for bitcoin decimal(16,8) and for other currencies decimal(10,2) , show me a way - please consider millions of records when you answering.</p>