在 SQL Server 中使用 FOR JSON AUTO 的问题答案

【问题标题】：Problem with using of FOR JSON AUTO in SQL Server在 SQL Server 中使用 FOR JSON AUTO 的问题
【发布时间】：2022-01-16 03:59:27
【问题描述】：

我在 SQL Server 数据库中使用FOR JSON AUTO，将我的查询结果转换为 JSON 格式。在我的查询中，我将 order 表加入了另外两个表。

SELECT
    orders.[Code], orders.[Total], orders.[Discount], 
    customer.[Name], customer.[PhoneNumber], 
    store.[Name], store.[Address]
FROM
    Orders orders 
INNER JOIN
    Customers customer ON (orders.[CustomerID] = customer.[ID]) 
INNER JOIN
    Stores store ON (orders.[StoreID] = store.[ID])
FOR JSON AUTO

结果：

[
  {
    "Code": "1528",
    "Total": 5000,
    "Discount": 20,
    "customer": [
      {
        "Name": "Alex",
        "PhoneNumber": "(548) 123-5555",
        "store": [
          {
            "Name": "Apple",
            "Address": "E. Santa rd"
          }
        ]
      }
    ]
  },
  {
    "Code": "1687",
    "Total": 3000,
    "Discount": 10,
    "customer": [
      {
        "Name": "John",
        "PhoneNumber": "(226) 354-7896",
        "store": [
          {
            "Name": "Sony",
            "Address": "W. Atlantic ave"
          }
        ]
      }
    ]
  }
]

但这不正确，因为在这种情况下客户和商店是兄弟，他们有相同的父母，他们都直接加入订单表，正确的JSON必须是这样的：

[
    {
        "Code": "1528",
        "Total": 5000,
        "Discount": 20,
        "customer": [
            {
                "Name": "Alex",
                "PhoneNumber": "(548) 123-5555"
            }
        ],
        "store": [
            {
                "Name": "Apple",
                "Address": "E. Santa rd"
            }
        ]
    },
    {
        "Code": "1687",
        "Total": 3000,
        "Discount": 10,
        "customer": [
            {
                "Name": "John",
                "PhoneNumber": "(226) 354-7896"
            }
        ],
        "store": [
            {
                "Name": "Sony",
                "Address": "W. Atlantic ave"
            }
        ]
    }
]

我该怎么做？ SQL中是否有任何选项？（我不想使用内部选择。）

【问题讨论】：

请添加这是什么数据库。

标签： sql json sql-server join

【解决方案1】：

如果Orders 和Customer 之间以及Orders 和Store 之间存在一对一的关系，那么您可以使用PATH 选项和点分隔的列名来生成所需的输出：

SELECT
    orders.[Code], orders.[Total], orders.[Discount], 
    customer.[Name] AS [Customer.Name], customer.[PhoneNumber] AS [Customer.PhoneNumber], 
    store.[Name] AS [Store.Name], store.[Address] AS [Store.Address]
FROM
    Orders orders 
INNER JOIN
    Customers customer ON (orders.[CustomerID] = customer.[ID]) 
INNER JOIN
    Stores store ON (orders.[StoreID] = store.[ID])
FOR JSON PATH

但如果存在一对多关系，则必须使用嵌套查询：

SELECT
    orders.[Code], orders.[Total], orders.[Discount], 
    (SELECT [Name], [PhoneNumber] FROM Customers WHERE Customers.ID=Orders.CustomerID FOR JSON AUTO) AS Customers,
    (SELECT [Name], [Address] FROM Stores WHERE Stores.ID=Orders.StoreID FOR JSON AUTO) AS Stores
FROM
    Orders orders 
FOR JSON AUTO

【讨论】：