一丶is 和 == 的区别 == 比较的是值 is 比较的是内存地址 #字符串 a = "abc" b = "abc" print(a == b) print(a is b) #数字 a = 123 b = 123 print(a == b) print(a is b) # 字典 a = {"a":1,"b":2,"c":3} b = {"a":1,"b":2,&qu…
1. 练习 数据: (1)需求1:统计有过连续3天以上销售的店铺有哪些,并且计算出连续三天以上的销售额 第一步:将每天的金额求和(同一天可能会有多个订单) SELECT sid,dt,SUM(money) day_money FROM v_orders GROUP BY sid,dt 第二步:给每个商家中每日的订单按时间排序并打上编号 SELECT sid,dt,day_money, ROW_NUMBER() OVER(PARTITION BY sid ORDER BY dt) rn FROM…
Services 简介和分类 A Service is an application component that can perform long-running operations in the background and does not provide a user interface. Another application component can start a service and it will continue to run in the background eve…
exec 不是表达式: python 2. x, 中的一个语句和 python 3. x. 中的一个函数它编译并立即计算一个字符串中包含的语句或者语句集. 例如: exec('print(5)') # prints 5. # exec 'print 5' if you use Python 2.x, nor the exec neither the print is a function there exec('print(5)\nprint(6)') # prints 5{newline}6.…
