如何使用Microsoft SQL Server 2016生成分层JSON数据? [英] How to generate hierarchical JSON data with Microsoft SQL Server 2016?

问题描述

我正在使用 Microsoft SQL Server 2016 .此版本支持JSON.

I'm using Microsoft SQL Server 2016. This version supports JSON.

我有一个人表，其中包含以下数据:

I have a Person table with the following data:

PersonId    FatherId    Name
1           NULL        4th Grand Father
2           1           3rd Grand Father
3           2           2nd Grand Father
4           3           Grand Father
5           4           Father
6           4           Uncle
7           6           Cousin
8           5           Brother
9           5           Me

我运行以下查询:

WITH Persons_CTE AS(
    SELECT PersonId, FatherId, Name FROM Persons WHERE FatherId IS NULL
    UNION ALL
    SELECT P.PersonId, P.FatherId, P.Name FROM Persons P JOIN Persons_CTE PCTE
    ON PCTE.PersonId = P.FatherId)

    SELECT P.Name as Name, PCTE.Name as Children FROM Persons_CTE PCTE LEFT JOIN Persons P
    ON P.PersonId = PCTE.FatherId 
    FOR JSON PATH

查询生成以下结果:

[
   {
      "Children":"4th Grand Father"
   },
   {
      "Name":"4th Grand Father",
      "Children":"3rd Grand Father"
   },
   {
      "Name":"3rd Grand Father",
      "Children":"2nd Grand Father"
   },
   {
      "Name":"2nd Grand Father",
      "Children":"Grand Father"
   },
   {
      "Name":"Grand Father",
      "Children":"Father"
   },
   {
      "Name":"Grand Father",
      "Children":"Uncle"
   },
   {
      "Name":"Uncle",
      "Children":"Cousin"
   },
   {
      "Name":"Father",
      "Children":"Brother"
   },
   {
      "Name":"Father",
      "Children":"Me"
   }
]

我希望查询结果为以下分层格式.我该怎么办?

I want the query result to the following hierarchical format. How can I do it?

[
  {
    "Name": "4th Grand Father",
    "Children": [
      {
        "Name": "3rd Grand Father",
        "Children": [
          {
            "Name": "2nd Grand Father",
            "Children": [
              {
                "Name": "Grand Father",
                "Children": [
                  {
                    "Name": "Father",
                    "children": [
                      {
                        "Name": "Brother"
                      },
                      {
                        "Name": "Me"
                      }
                    ]
                  },
                  {
                    "Name": "Uncle",
                    "children": [
                      {
                        "Name": "Cousin"
                      }
                    ]
                  }
                ]
              }
            ]
          }
        ]
      }
    ]
  }
]

推荐答案

不幸的是，递归CTe无法用于生成分层json.递归CTE的输出仍然是平坦的结果.

Unfortunately, recursive CTe cannot be used to generate hierarchical json . Output of recursive CTE is still flat result.

创建分层输出的唯一方法是为每个级别创建单独的CTE，然后使用FOR JSON AUTO加入

The only way to create hierarchical output is to create separate CTE for each level and then join the using FOR JSON AUTO

准备表格:

declare @t table (PersonId int, FatherId int, Name nvarchar(20));

insert into @t(PersonId, FatherId, Name)
values
(1, NULL, '4th Grand Father'),
(2, 1, '3rd Grand Father'),
(3, 2, '2nd Grand Father'),
(4, 3, 'Grand Father'),
(5, 4, 'Father'),
(6, 4, 'Uncle'),
(7, 6, 'Cousin'),
(8, 5, 'Brother'),
(9, 5, 'Me');

-分层查询:

WITH
Persons_CTE1 AS(
    SELECT PersonId, FatherId, Name FROM @t WHERE FatherId IS NULL
),
Persons_CTE2 AS(
    SELECT P.PersonId, P.FatherId, P.Name
    from @t P
    WHERE P.FatherId IN (SELECT PersonId FROM Persons_CTE1)
),
Persons_CTE3 AS(
    SELECT P.PersonId, P.FatherId, P.Name
    from @t P
    WHERE P.FatherId IN (SELECT PersonId FROM Persons_CTE2)
),
Persons_CTE4 AS(
    SELECT P.PersonId, P.FatherId, P.Name
    from @t P
    WHERE P.FatherId IN (SELECT PersonId FROM Persons_CTE3)
),
Persons_CTE5 AS(
    SELECT P.PersonId, P.FatherId, P.Name
    from @t P
    WHERE P.FatherId IN (SELECT PersonId FROM Persons_CTE4)
),
Persons_CTE6 AS(
    SELECT P.PersonId, P.FatherId, P.Name
    from @t P
    WHERE P.FatherId IN (SELECT PersonId FROM Persons_CTE5)
)
select Persons_CTE1.Name, Persons_CTE2.Name, Persons_CTE3.Name,
       Persons_CTE4.Name, Persons_CTE5.Name, Persons_CTE6.Name
from Persons_CTE1
    LEFT JOIN Persons_CTE2
        ON Persons_CTE2.FatherId = Persons_CTE1.PersonId
    LEFT JOIN Persons_CTE3
        ON Persons_CTE3.FatherId = Persons_CTE2.PersonId
    LEFT JOIN Persons_CTE4
        ON Persons_CTE4.FatherId = Persons_CTE3.PersonId
    LEFT JOIN Persons_CTE5
        ON Persons_CTE5.FatherId = Persons_CTE4.PersonId
    LEFT JOIN Persons_CTE6
        ON Persons_CTE6.FatherId = Persons_CTE5.PersonId
FOR JSON AUTO

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