H . using a common table expression to selectively step through a recursive relationship in a select statement H .使用公用表表达式来有选择地执行select语句中的递归操作
2.
There is an intrinsic recursive relationship in the bill of material structure that indicates the relationship between a parent product and the components that make up that product 物料清单结构本身是一种嵌套结构,指示父级产品和构成该产品的组件之间的关系。