SqlServer使用公用表表达式（CTE）实现无限级树形构建_Sql Server

SqlServer使用公用表表达式（CTE）实现无限级树形构建

2020-05-22 15:13BruceAndLee Sql Server

本文给大家分享的是sqlserver中使用公用表表达式（CTE）实现无限级树形构建的详细代码，非常的简单实用，有需要的小伙伴可以参考下

SQL Server 2005开始，我们可以直接通过CTE来支持递归查询,CTE即公用表表达式

公用表表达式（CTE），是一个在查询中定义的临时命名结果集将在from子句中使用它。每个CTE仅被定义一次（但在其作用域内可以被引用任意次），并且在该查询生存期间将一直生存。可以使用CTE来执行递归操作。

				?

									DECLARE @Level INT=3

									;WITH cte_parent(CategoryID,CategoryName,ParentCategoryID,Level)

									AS

									(

									  SELECT category_id,category_name,parent_category_id,1 AS Level

									  FROM TianShenLogistic.dbo.ProductCategory WITH(NOLOCK)

									 WHERE category_id IN

									 (

									 SELECT category_id 

									 FROM TianShenLogistic.dbo.ProductCategory 

									 WHERE parent_category_id=0

									 )

									  UNION ALL

									  SELECT b.category_id,b.category_name,b.parent_category_id,a.Level+1 AS Level

									  FROM TianShenLogistic.dbo.ProductCategory b

									  INNER JOIN cte_parent a

									  ON a.CategoryID = b.parent_category_id

									)

									SELECT

									 CategoryID AS value,

									 CategoryName as label,

									 ParentCategoryID As parentId,

									 Level

									FROM cte_parent WHERE Level <=@Level;

									public static List<LogisticsCategoryTreeEntity> GetLogisticsCategoryByParent(int? level)

									    {

									      if (level < 1) return null;

									      var dataResult = CategoryDA.GetLogisticsCategoryByParent(level);

									      var firstlevel = dataResult.Where(d => d.level == 1).ToList();

									      BuildCategory(dataResult, firstlevel);

									      return firstlevel;

									    }

									    private static void BuildCategory(List<LogisticsCategoryTreeEntity> allCategoryList, List<LogisticsCategoryTreeEntity> categoryList)

									    {

									      foreach (var category in categoryList)

									      {

									        var subCategoryList = allCategoryList.Where(c => c.parentId == category.value).ToList();

									        if (subCategoryList.Count > 0)

									        {

									          if (category.children == null) category.children = new List<LogisticsCategoryTreeEntity>();

									          category.children.AddRange(subCategoryList);

									          BuildCategory(allCategoryList, category.children);

									        }

									      }

									    }