This is a part of this question . I have Departments table which uses HierarchyId to store hierarchical data.

I want to get this table as JSON for my TreeView on front side.

What I did:

CREATE FUNCTION dbo.GetDepartmentAsJson
    (@departmentId hierarchyid, 
     @IsRoot int)
RETURNS nvarchar(max)
AS
BEGIN
    DECLARE @Json NVARCHAR(MAX) = '{}',
            @Id int,
            @Name varchar(50),
            @Children NVARCHAR(MAX) = '{}',
            @Hierar Hierarchyid

    SET @Json = (SELECT 
                     t.Id, t.HierarchyId, t.Name,
                     children = JSON_QUERY(dbo.GetDepartmentAsJson(t.HierarchyId, 2))
                 FROM Departments t
                 WHERE t.HierarchyId <> @departmentId
                   AND t.HierarchyId.IsDescendantOf(@departmentId) = 1
                 FOR JSON PATH);

    IF (@IsRoot = 1) 
    BEGIN
        SELECT
            @Id = t.Id,
            @Hierar = t.HierarchyId,
            @Name = t.Name
        FROM 
            Departments t
        WHERE 
            t.HierarchyId = @departmentId;

        SET @Json = 
        '{"Id":"'   CONVERT(varchar(7), @Id)  
        '","HierarchyId":"'   @Hierar.ToString()   
        '","Name":"'   @Name   
        '","Children":'   CAST(@Json AS NVARCHAR(MAX))   '}';
        SET @IsRoot = 2;
    END

    RETURN @Json;
END;

Result:

 {
  "Id": "1",
  "HierarchyId": "/",
  "Name": "MHz",
  "Children": [
    {
      "Id": 2,
      "HierarchyId": "/2/",
      "Name": "Finance",
      "Children": [
        {
          "Id": 6,
          "HierarchyId": "/2/6/",
          "Name": "Accountant"
        }
      ]
    },
    /* This should not be listed because already included as a child in Finance */
    {
      "Id": 6,
      "HierarchyId": "/2/6/",
      "Name": "Accountant"
    },
    {
      "Id": 3,
      "HierarchyId": "/3/",
      "Name": "IT",
      "Children": [
        {
          "Id": 4,
          "HierarchyId": "/3/4/",
          "Name": "Software Development"
        },
        {
          "Id": 5,
          "HierarchyId": "/3/5/",
          "Name": "QA"
        }
      ]
    },
    /* They both should not be listed because already included as a child in IT */
    {
      "Id": 4,
      "HierarchyId": "/3/4/",
      "Name": "Software Development"
    },
    {
      "Id": 5,
      "HierarchyId": "/3/5/",
      "Name": "QA"
    }
  ]
}

How can I exclude this child elements which have been already listed in parent element?

CodePudding user response：

You should check the level of the descendant as well

CREATE FUNCTION dbo.GetDepartmentAsJson(@departmentId hierarchyid, @level int)
RETURNS nvarchar(max)
AS
BEGIN
DECLARE @Json NVARCHAR(MAX) = '{}',
    @Id int,
    @Name varchar(50),
    @Childeren NVARCHAR(MAX) = '{}',
    @Hierar Hierarchyid

    SET @Json = (SELECT
    t.Id,
    t.HierarchyId,
    t.Name,
    children = JSON_QUERY(dbo.GetDepartmentAsJson(t.HierarchyId, @level   1))
    FROM Departments t
    WHERE t.HierarchyId <> @departmentId
    AND t.HierarchyId.IsDescendantOf(@departmentId) = 1 and t.HierarchyId.GetLevel() =  @level   1
    FOR JSON PATH);

    IF(@level = 0) 
    BEGIN
        SELECT
        @Id = t.Id,
        @Hierar = t.HierarchyId,
        @Name = t.Name
        FROM Departments t
        WHERE t.HierarchyId = @departmentId;

        SET @Json = 
        '{"Id":"'   CONVERT(varchar(7), @Id)  
        '","HierarchyId":"'   @Hierar.ToString()   
        '","Name":"'   @Name   
        '","Children":'   CAST(@Json AS NVARCHAR(MAX))   '}';
    END

    return @Json;

  END;

The root of the hierarchy is level 0, so select dbo.GetDepartmentAsJson ('/', 0)

db<>fiddle