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json - 如何使用 FOR JSON 构建这种格式的 JSON？

问题描述

我想使用FOR JSON为 HTTP Post 调用构建数据有效负载。我的源表可以用这个片段重新创建：

drop table if exists #jsonData;
drop table if exists #jsonColumns;

select
    'carat' [column] 
into #jsonColumns
union
select 'cut' union
select 'color' union
select 'clarity' union
select 'depth' union
select 'table' union
select 'x' union
select 'y' union
select 'z'

select
    0.23 carat
    ,'Ideal' cut
    ,'E' color
    ,'SI2' clarity
    ,61.5 depth
    ,55.0 [table]
    ,3.95 x
    ,3.98 y
    ,2.43 z
into #jsonData
union
select 0.21,'Premium','E','SI1',59.8,61.0,3.89,3.84,2.31 union
select 0.29,'Premium','I','VS2',62.4,58.0,4.2,4.23,2.63 union
select 0.31,'Good','J','SI2',63.3,58.0,4.34,4.35,2.75
;

数据需要格式化如下：

{
    "columns":["carat","cut","color","clarity","depth","table","x","y","z"],
    "data":[
        [0.23,"Ideal","E","SI2",61.5,55.0,3.95,3.98,2.43],
        [0.21,"Premium","E","SI1",59.8,61.0,3.89,3.84,2.31],
        [0.23,"Good","E","VS1",56.9,65.0,4.05,4.07,2.31],
        [0.29,"Premium","I","VS2",62.4,58.0,4.2,4.23,2.63],
        [0.31,"Good","J","SI2",63.3,58.0,4.34,4.35,2.75]
    ]
}

到目前为止，我的尝试如下：

select
    (select * from #jsonColumns for json path) as [columns],
    (select * from #jsonData for json path) as [data]
for json path, without_array_wrapper

但是，这会返回对象数组而不是值，如下所示：

{
    "columns":[
        {"column":"carat"},
        {"column":"clarity"},
        {"column":"color"},
        {"column":"cut"},
        {"column":"depth"},
        {"column":"table"},
        {"column":"x"},
        {"column":"y"},
        {"column":"z"}
    ]...
}

如何将数组限制为仅显示值？

标签： jsonsql-serversql-server-2016for-json

解决方案

老实说，使用字符串聚合而不是使用 JSON 功能似乎会更容易。

因为您使用的是 SQL Server 2016，所以您无权访问STRING_AGGor CONCAT_WS，因此代码要长很多。您必须使用FOR XML PATHand手动插入所有分隔符（为什么表达式中STUFF有这么多）。这导致以下结果：','CONCAT

DECLARE @CRLF nchar(2) = NCHAR(13) + NCHAR(10);

SELECT N'{' + @CRLF +
       N'    "columns":[' + STUFF((SELECT ',' + QUOTENAME(c.[name],'"')
                                   FROM tempdb.sys.columns c
                                        JOIN tempdb.sys.tables t ON c.object_id = t.object_id
                                   WHERE t.[name] LIKE N'#jsonData%' --Like isn't needed if not a temporary table. Use the literal name.
                                   ORDER BY c.column_id ASC
                                   FOR XML PATH(N''),TYPE).value('.','nvarchar(MAX)'),1,1,N'') + N'],' + @CRLF +
       N'    "data":[' + @CRLF +
       STUFF((SELECT N',' + @CRLF +
                     N'       ' + CONCAT('[',JD.carat,',',QUOTENAME(JD.cut,'"'),',',QUOTENAME(JD.color,'"'),',',QUOTENAME(JD.clarity,'"'),',',JD.depth,',',JD.[table],',',JD.x,',',JD.y,',',JD.z,']')
              FROM #jsonData JD
              ORDER BY JD.carat ASC
              FOR XML PATH(N''),TYPE).value('.','nvarchar(MAX)'),1,3,N'') + @CRLF +
      N'    ]' + @CRLF +
      N'}';

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