完善和测试了查询功能
Merge branch 'master' of
ssh://git@github.com/minusone13/InvoicingSystem.git

Conflicts:
	LevelStrategyPO.txt
	PaymentPO.txt
	ReachStrategyPO.txt
	Stock.ser
	User.ser
Merge branch 'master' of
ssh://git@github.com/minusone13/InvoicingSystem.git

Conflicts:
	LevelStrategyPO.txt
	PaymentPO.txt
	ReachStrategyPO.txt
	SaleSheetPO.txt