Based on mysql5.7 and PyQt5, it's developed for financial staff to process data in a more convenient way.
180302：to solve the problem of calculation in 成本明细, where negative numbers and decimals can't be ca-
lculated correctly.
Plan1:to use mysql's type--decimal(a,b) to solve the problem; to check whether decimals(without other ch-
aracters) are input before data storing.
Plan2:to write another routine to process negative or decimals calculation.
180303:choose Plan1 and finish it roughly.