摘要：每个城市中属于每种类别的消费者的数量select city,no_orders,upto_two_orders,more_than_two_orders from(select c.customerid,city,case when count(orderid) = 0 then 'no_orders' when count(orderid) <=2 then 'upto_two_orders' when count(orderid) >2 then 'more_than_two_orders'end as categoryfrom 阅读全文

摘要：SQLNorthWind表格说明-------------------------Categories:种类表 --相应字段:CategoryID :类型ID；CategoryName:类型名;Description:类型说明;Picture:产品样本-------------------------CustomerCustomerDemo:客户类型表1--相应字段：CustomerID：客户ID；CustomerTypeID：客户类型ID-------------------------CustomerDemographics:客户类型表2--相应字段：CustomerTypeID：客户类型 阅读全文

摘要：--表结构：if exists (select * from sysobjects where id = OBJECT_ID('[表1]') and OBJECTPROPERTY(id, 'IsUserTable') = 1) DROP TABLE [表1] CREATE TABLE [表1] ( [ID] [int] NULL , [NAME] [varchar] (10) NULL , [QQ] [varchar] (10) NULL , [PHONE] [varchar] (20) NULL )INSERT [表1] ( [ID] , [NAME] , [ 阅读全文

摘要：经常写一些联合查询，联合一多了，代码就成倍的增加，时间一长，连我自己也看不懂到底是什么意思了。做Oracle 的时候，就看到有个 WITH, 不过没有深入的看，就会 WITH 一个出来。前几天又想用这个WITH,于是细心的查查了，原来 WITH 多个 联系查询的语法是这样的：WITH PPC AS ( SELECT A.* FROM( SELECT ROW_NUMBER() OVER (PARTITION BY PPCMemberID ORDER BY CreatedOn DESC) AS RN, PPCMemberID,PPC,DailyBudget,CreatedOn FROM CS... 阅读全文

摘要：第二种简单的方法是运用CheckForIllegalCrossThreadCalls，在主窗体的构造函数中加上以下代码即可:Control.CheckForIllegalCrossThreadCalls = false; 阅读全文

摘要：修改列类型Alter table tb_SystemConfigOption alter column CreateDate smalldatetime null 阅读全文