摘要： keycode 8 = BackSpace BackSpace keycode 9 = Tab Tab keycode 12 = Clear keycode 13 = Enter keycode 16 = Shift_L keycode 17 = Control_L keycode 18 = Alt_L keycode 19 = Pause keycode 20 = Caps_Lock keyco... 阅读全文

摘要： Coalesce:语法 COALESCE ( expression [ ,...n ] ) 判断里面的选项值，输出最近一个非NULL的值，当全部为NULL返回NULL值NullIF()语法 NULLIF ( expression1 , expression2 )HavingIntersct两张表相同的数据Except两张表不同的数据Create Table As 阅读全文