在开发中遇到一个问题,在mysql中字段都为varchar型,但是有的没有值查出来是NULL,有的查出来是空。 先来看一下mysql中的NULL和empty String的区别: 1.A NULL value represents the absence of a value for a record in a field (others softwares call it also a mis
G了半天,才找到点线索,原因: Adding the root view to your UIWindow can be complicated since the window always underlaps the status bar. The frame of your root view must therefore be reset to [[UIScreen mainScr