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我正在尝试从我的 SQL 数据库（兼容级别 140）构建一个 JSON 序列化的键/值对项列表。诀窍是值可以是任何东西：数字、字符串、null 或其他 JSON 对象。

它应该看起来像这样：

[{"key":"key1","value":"A String"},{"key":"key2","value":{"InnerKey":"InnerValue"}}]

但是，SQL 似乎迫使我选择一个字符串或一个对象。

SELECT
       [key] = kvp.[key],
       [value] = CASE
              WHEN ISJSON(kvp.[value]) = 1 THEN JSON_QUERY(kvp.[value])
              ELSE '"' + kvp.[value] + '"'  -- See note below
              END
FROM (VALUES
        ('key1', 'This value is a string')
       ,('key2', '{"description":"This value is an object"}')
       ,('key3', '["This","value","is","an","array","of","strings"]')
       ,('key4', NULL)

       -- Without these lines, the above 4 work fine; with either of them, even those 4 are broken
       --,('key5', (SELECT [description] = 'This value is a dynamic object' FOR JSON PATH, WITHOUT_ARRAY_WRAPPER))
       --,('key6', JSON_QUERY((SELECT [description] = 'This value is a dynamic object' FOR JSON PATH, WITHOUT_ARRAY_WRAPPER)))
) AS kvp([key], [value])
FOR JSON PATH

我是在尝试做一些 SQL 无法支持的事情，还是我只是缺少正确的语法来完成这项工作？

*请注意，似乎没有必要添加双引号。但没有这些，SQL 无法包装字符串并生成错误的 JSON：

[{"key":"key1","value":This value is a string},...
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1 回答 1

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如果您的查询被修改为此，它的工作原理：

SELECT
   [key] = kvp.[key],
   [value] = ISNULL(
          JSON_QUERY(CASE WHEN ISJSON(kvp.[value]) = 1 THEN kvp.[value] END),
          '"' + STRING_ESCAPE(kvp.[value], 'json') + '"'
   )
FROM (VALUES
   ('key1', 'This value is a "string"')
   ,('key2', '{"description":"This value is an object"}')
   ,('key3', '["This","value","is","an","array","of","strings"]')
   ,('key4', NULL)

   -- These now work
   ,('key5', (SELECT [description] = 'This value is a dynamic object' FOR JSON PATH, WITHOUT_ARRAY_WRAPPER))
   ,('key6', JSON_QUERY((SELECT [description] = 'This value is a dynamic object' FOR JSON PATH, WITHOUT_ARRAY_WRAPPER)))
) AS kvp([key], [value])
FOR JSON PATH, INCLUDE_NULL_VALUES

当然，如果value是int. 另外，我真的无法解释为什么你的不起作用。

于 2017-12-15T15:02:48.687 回答