中通过原子建立分子查询覆盖

主动作为 我会在等式中引入一个表格UDF，如清单C所示。注意，我可以用两种方法调用函数：提交CustomerID将表格限定为那个顾客的订单，或提交一个NULL获得所有顾客订单清单。如果我提交CustomerID，那么订单清单就出现在OrderDate中；如果我提交NULL，清单就被分组并在CustomerID中由OrderDate排序。 set ANSI_NULLS ONset QUOTED_IDENTIFIER ONgo-- =============================================-- Author: Arthur Fuller-- Create date: 23 Aug 2006-- Description: Table UDF to return Order Totals by Customer-- Example: SELECT * FROM stomerOrderTotals_fnt(\'VINET\')-- Example: SELECT * FROM stomerOrderTotals_fnt(NULL)-- Notes: This udf is designed to serve two-- purposes. Pass a CustomerID to limit the rows to -- that customer, or pass nothing to get all customers-- =============================================ALTERFUNCTION [dbo].[CustomerOrderTotals_fnt]( -- Add the parameters for the function here @CustomerID varchar(5)=NULL)RETURNS TABLE ASRETURN ( -- Add the SELECT statement with parameter references here SELECTTOP 100 PERCENT stomerID, panyName, derID, derDate, derDetailsSumByOrderID_talAmount FROM stomers INNERJOIN ders ON stomerID = stomerID INNERJOIN derDetailsSumByOrderID_vue ON derID = derDetailsSumByOrderID_derID WHERE stomerID = @CustomerID OR @CustomerID ISNULL ORDERBY derDate )--try it with these:--SELECT * FROM stomerOrderTotals_fnt(\'VINET\')--SELECT * FROM stomerOrderTotals_fnt(NULL)

清单C-- ================================================-- Template generated from Template Explorer using:-- Create Inline Function (New Menu).SQL---- Use the Specify Values for Template Parameters -- command (Ctrl-Shift-M) to fill in the parameter -- values below.---- This block of comments will not be included in-- the definition of the function.-- ================================================SET ANSI_NULLS ONGOSET QUOTED_IDENTIFIER ONGO-- =============================================-- Author: Arthur Fuller-- Create date: 23 Aug 2006-- Description: Return total sales by Customer-- Example:-- SELECT CustomerID, CustomerTotal-- FROM stomerGrandTotal_fnt(null)-- SELECT CustomerID, CustomerTotal-- FROM stomerGrandTotal_fnt(\'VINET\')-- SELECT CustomerID, CustomerTotal-- FROM stomerGrandTotal_fnt(\'VINET\')-- =============================================CREATEFUNCTION CustomerGrandTotal_fnt ( @CustomerID varchar(5) )RETURNS TABLE ASRETURN ( -- Add the SELECT statement with parameter references here SELECTTOP 100 PERCENT CustomerID, SUM(TotalAmount)AS CustomerTotal FROM stomerOrderTotals_fnt(@CustomerID) WHERE stomerOrderTotals_stomerID = @CustomerID OR @CustomerID ISNULL GROUPBY CustomerID ORDERBY CustomerID)GO

清单D更深入一步，我每个顾客打印一行，用一列显示每名顾客的总销售额。查看清单D。并不是所有项目都得到组合。在最外层，我能够以两种方式调用这个函数：提交合法CustomerID或UNLL。以下是它们各自的实例： SELECT CustomerID, CustomerTotalFROM stomerGrandTotal_fnt(null)SELECT CustomerID, CustomerTotalFROM stomerGrandTotal_fnt(\'VINET\')

现在你有了一组精确的工具来帮助你挖掘适当层次的细节。计算列tendedAmount隐藏了一个复杂层次，从那我又深入到我希望隐藏的细节。这就是我把这些对象叫做原子和分子查询的原因。我使用“查询”一词来概括这样一个事实，即讨论的对象是视图还是表格UDF并不重要。（虽然由于命名规则，suffix _fnt表示一个表格UDF，而suffix _vue表示一个视图。） 必须承认，Northwind数据库中没有大量的行，但我认为这种技巧可以得到很好地扩充。更为重要的是，我喜欢它提供的粒度。我能够做我想做的，并按要求重新使用或重新组合原子。