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SqlServer使用公用表表達(dá)式（CTE）實(shí)現(xiàn)無(wú)限級(jí)樹(shù)形構(gòu)建

 更新時(shí)間：2017年08月28日 08:39:17   作者：BruceAndLee  
本文給大家分享的是sqlserver中使用公用表表達(dá)式（CTE）實(shí)現(xiàn)無(wú)限級(jí)樹(shù)形構(gòu)建的詳細(xì)代碼，非常的簡(jiǎn)單實(shí)用，有需要的小伙伴可以參考下

SQL Server 2005開(kāi)始，我們可以直接通過(guò)CTE來(lái)支持遞歸查詢,CTE即公用表表達(dá)式

公用表表達(dá)式（CTE），是一個(gè)在查詢中定義的臨時(shí)命名結(jié)果集將在from子句中使用它。每個(gè)CTE僅被定義一次（但在其作用域內(nèi)可以被引用任意次），并且在該查詢生存期間將一直生存?？梢允褂肅TE來(lái)執(zhí)行遞歸操作。

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);
        }
      }
    }

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