我正在尝试对多个 select 语句背后的推理进行正面和反面。换句话说,重点是什么?注意:我对 T-SQL 非常熟悉……我已经从 SQL Server 的维护方面转移到它的开发方面。以下是让我感到困惑的代码(部分):
SELECT DISTINCT id
,NAME
,TypeCode
,ProductId
,ProductName
,LocationCode
,County
,STATE
,RecommendationType
,PackageName
FROM (
SELECT c.Id
,C.NAME
,p.Typecode
,p.ProductId
,p.Productname
,p.LocationCode
,p.County
,p.STATE
,'Appened' AS RecommendationType
,PackageName
FROM (
SELECT op.*
,t.i.value('@ProductId', 'varchar(50)') AS productId
,t.i.value('@Name', 'varchar(50)') AS Product
FROM (
SELECT pg.CustomerId
,pg.NAME AS PackageName
,pg.runtimedefinition.query('/PackageDefinition/Products') AS CList
FROM product.package pg WITH (NOLOCK)
) op
CROSS APPLY clist.nodes('Products/Task[@xsi:type="ProductTask"]') t(i)
) m
请记住...此代码是部分代码。
谢谢!!