如何使用 FOR JSON 构建这种格式的 JSON？

Question

我想使用 FOR JSON 为 HTTP Post 调用构建数据负载。我的源表可以用这个 sn-p 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 objects 数组而不是 values，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？

Answer 1

老实说，使用字符串聚合而不是使用 JSON 功能似乎会更容易。

由于您使用的是 SQL Server 2016，因此您无权访问 STRING_AGG 或 CONCAT_WS，因此代码较长。您必须改用FOR XML PATH 和STUFF 并手动插入所有分隔符（为什么CONCAT 表达式中有这么多','）。结果如下：

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'}';

DB<>Fiddle