{"id":801,"date":"2014-05-06T09:46:13","date_gmt":"2014-05-06T13:46:13","guid":{"rendered":"http:\/\/binaryworld.net\/blogs\/?p=801"},"modified":"2015-12-01T16:37:36","modified_gmt":"2015-12-01T21:37:36","slug":"sql-parent-child-query-example-recursive-cte-hierarchy","status":"publish","type":"post","link":"https:\/\/binaryworld.net\/blogs\/sql-parent-child-query-example-recursive-cte-hierarchy\/","title":{"rendered":"SQL Server parent child query example using recursive CTE (Common Table Expression)"},"content":{"rendered":"

Many times we have to write recursive parent child\u00a0query <\/em><\/strong>(Multiple levels of Parent-Child Links)\u00a0 in SQL Server. There are multiple approaches to achieve this<\/p>\n

    \n
  1. Using Hierarchy ID builtin CLR datatype<\/strong> in SQL Server 2008 or higher (not ion sql server 2000, 2005)<\/li>\n
  2. Using CTE (Common Table Expression)<\/strong> (sql server 2005 or higher)<\/li>\n
  3. Custom recursive function or stored proc.<\/li>\n<\/ol>\n

    I think Most effective way parent child query<\/strong> to get unknown levels of hierarchy is using…. Common Table Expression (CTE)<\/strong> feature of SQL Server (introduced in SQL Server 2005).<\/p>\n

    Common examples of multiple levels of nested parent child query<\/em> are … getting\u00a0parent branches of\u00a0selected employee, navigate through org chart hierarchy using sql<\/em>, navigate through product hierarchy<\/em> using t-sql<\/p>\n

    Below is complete T-SQL example on how to write\u00a0parent child query<\/em> using CTE (2 examples… Find all Children of selected Parent node, Find all Parent Nodes or Selected Child Node)<\/p>\n

    Basic syntax of SQL CTE like below<\/p>\n

    WITH Recursive-CTE-Query<\/em> AS (
    \u00a0 {Anchor Query}
    \u00a0 UNION ALL
    \u00a0 {Query joined to Recursive-CTE-Query<\/em>}
    )
    SELECT * FROM Recursive-CTE-Query<\/em><\/p>\n

    Here is full example of SQL Server CTE to get hirarchy of parent child nodes stored in a table.<\/p>\n

    Example of recursive parent child query in SQL Server using CTE (Common Table Expression)<\/h3>\n
    create table #ParentChildTable \r\n(nodeID int not null ,parentNodeID int null ,ClassType varchar(100) not null\r\n)\r\ngo\r\n\r\ninsert into #ParentChildTable values(1,null,'Vehicle')\r\ninsert into #ParentChildTable values(2,1,'GroundVehicle')\r\ninsert into #ParentChildTable values(3,1,'AirVehicle')\r\ninsert into #ParentChildTable values(4,2,'Car')\r\ninsert into #ParentChildTable values(5,2,'Truck')\r\ninsert into #ParentChildTable values(6,2,'FlyingCar')\r\ninsert into #ParentChildTable values(7,4,'SUV')\r\ninsert into #ParentChildTable values(8,4,'VAN')\r\ninsert into #ParentChildTable values(9,8,'FordWindStar')\r\ninsert into #ParentChildTable values(10,3,'Airplane')\r\ninsert into #ParentChildTable values(11,4,'BMW-325')\r\n\r\n go\r\n\r\n --\/\/Find all parent nodes of specified Child Node(s)\r\n;WITH Heirarchy --\/\/Create CTE which can be called recursively\r\nAS\r\n(\r\n   SELECT Path=cast(T1.ClassType + '-' as varchar(1000)), Level=1, T1.NodeID,T1.ParentNodeID,T1.ClassType FROM #ParentChildTable T1\r\n   WHERE T1.NodeID=9 -- or -- T1.NodeID IN (9,10) --\/\/<< pass child node ID HERE\r\n   UNION ALL\r\n   SELECT Path1=cast(TH.Path + T1.ClassType + '-' as varchar(1000)),Level=TH.Level+1, T1.NodeID,T1.ParentNodeID,T1.ClassType\r\n   FROM #ParentChildTable T1 INNER JOIN Heirarchy TH ON TH.parentNodeID = T1.NodeID --<< Child to Parent \r\n)\r\nselect * from Heirarchy\r\n\r\n --\/\/Find all child nodes of Specified parent Node\r\n;WITH Heirarchy --\/\/Create CTE which can be called recursively\r\nAS\r\n(\r\n   SELECT Path=cast(T1.ClassType + '-' as varchar(1000)), Level=1, T1.NodeID,T1.ParentNodeID,T1.ClassType FROM #ParentChildTable T1\r\n   WHERE T1.NodeID=1 -- or -- T1.NodeID IN (9,10) --\/\/<< pass parent node ID HERE\r\n   UNION ALL\r\n   SELECT Path=cast(TH.Path + T1.ClassType + '-' as varchar(1000)),Level=TH.Level+1, T1.NodeID,T1.ParentNodeID,T1.ClassType\r\n   FROM #ParentChildTable T1 INNER JOIN Heirarchy TH ON TH.NodeID = T1.ParentNodeID --<< Parent to Child\r\n)\r\nselect * from Heirarchy \r\n\r\ngo\r\ndrop table #ParentChildTable \r\ngo\r\n\r\nHere is the output when you run these two queries<\/pre>\n
    \"How<\/a>
    How to get parent child relationship using recursive CTE query<\/figcaption><\/figure>\n
     <\/p>\n
    \u00a0Click here<\/a> to learn more about CTE on MSDN<\/p>\n","protected":false},"excerpt":{"rendered":"
    Many times we have to write recursive parent child\u00a0query (Multiple levels of Parent-Child Links)\u00a0 in SQL Server. There are multiple approaches to achieve this Using Hierarchy ID builtin CLR datatype in SQL Server 2008 or higher (not ion sql server …<\/p>\n
      SQL Server parent child query example using recursive CTE (Common Table Expression)<\/span> Read More »<\/a><\/p>\n","protected":false},"author":1,"featured_media":817,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[27,35],"tags":[158,130],"yoast_head":"\r\nSQL Server parent child query example using recursive CTE (Common Table Expression) - BinaryWorld Blog<\/title>\r\n<meta name=\"description\" content=\"This article explains how to write a simple and efficient parent child query using CTE (sql server recursive query technique)\" \/>\r\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\r\n<link rel=\"canonical\" href=\"https:\/\/binaryworld.net\/blogs\/sql-parent-child-query-example-recursive-cte-hierarchy\/\" \/>\r\n<meta property=\"og:locale\" content=\"en_US\" \/>\r\n<meta property=\"og:type\" content=\"article\" \/>\r\n<meta property=\"og:title\" content=\"SQL Server parent child query example using recursive CTE (Common Table Expression) - 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