JSON_MODIFY 不适用于可变参数

Question

我有一个修改一些 JSON 的 SQL 查询。我正在遍历数据并根据迭代修改部分 JSON。

为此，我需要将可变参数传递给 JSON_MODIFY，但由于某种原因，它不起作用！

SET @json = JSON_MODIFY(@ProData, '$.' + @ProKey + '.hasAnswer', CAST(1 as BIT))

我也尝试将整个表达式作为变量传递：

DECLARE @hasAnswerPath VARCHAR(100);
SET @hasAnswerPath = '$.' + @ProKey + '.hasAnswer';
SET @json = JSON_MODIFY(@ProData, @hasAnswerPath, CAST(1 as BIT))

但是它有相同的输出，hasAnswer被添加到JSON的根而不是@ProKey指定的元素中。

这很好用：

SET @json = JSON_MODIFY(@ProData, '$.SomeName1.hasAnswer', CAST(1 as BIT))

就像@ProKey 被忽略了。

完整查询：

BEGIN TRAN

DECLARE @ProID as uniqueidentifier;
DECLARE @ProData as nvarchar(max);
DECLARE @ProKey as varchar(200);

DECLARE ProCursor CURSOR FOR
    SELECT Id, [Data] FROM [dbo].[PRO]

OPEN ProCursor;
FETCH NEXT FROM ProCursor INTO @ProID, @ProData;
WHILE @@FETCH_STATUS = 0
BEGIN
    DECLARE @json NVARCHAR(max);

    DECLARE DataCursor CURSOR FOR
        SELECT [key] FROM OPENJSON(@ProData) WHERE type = 5; --5 is object data
        
    OPEN DataCursor;
    FETCH NEXT FROM DataCursor INTO @ProKey;
    WHILE @@FETCH_STATUS = 0
    BEGIN
        SET @json=JSON_MODIFY(@ProData, '$.' + @ProKey + '.hasAnswer', CAST(1 as BIT))
        SET @json=JSON_MODIFY(@json,'$.' + @ProKey + '.questionType','intro')
        
        FETCH NEXT FROM DataCursor INTO @ProKey;
    END;

    UPDATE [dbo].[PRO]
    SET [Data] = @json
    WHERE Id = @ProID

    PRINT @json

    CLOSE DataCursor;
    DEALLOCATE DataCursor;

    FETCH NEXT FROM ProCursor INTO @ProID, @ProData;
END
CLOSE ProCursor;
DEALLOCATE ProCursor;

ROLLBACK

示例 JSON：

 {
     "SomeName1": {
        "header": "Some text",
        "answer": {
            "type": "specified",
            "numberValue": 1.0
        }
     },
     "SomeName2": {
        "header": "Some text",
        "answer": {
            "type": "specified",
            "numberValue": 4.0
         }
     },
     "SomeName3": {
         "header": "Some text",
         "answer": {
             "type": "specified",
             "numberValue": 2.0
        }
     }
 }

预期结果：

},
    "SomeName1": {
        "header": "Some text",
        "answer": {
            "type": "specified",
            "numberValue": 1.0
        }
        "hasAnswer": true,
        "questionType": "intro",
     }
}

实际结果：

},
    "SomeName1": {
            "header": "Some text",
            "answer": {
                "type": "specified",
                "numberValue": 1.0
            }
         }
     },
     "hasAnswer":true,
     "questionType":"intro"
 }

我在这里做错了什么？

Answer 1

您似乎无意中覆盖了变量：

-- first iteration

SET @json=JSON_MODIFY(@ProData, '$.' + @ProKey + '.hasAnswer', CAST(1 as BIT))
-- @json contains the @prodata after modification to first key (@prodata itself is not changed)

SET @json=JSON_MODIFY(@json,'$.' + @ProKey + '.questionType','intro')
-- @json (its first key to be more precise) is modified further

但在下一次迭代中，此行会将修改后的 @json 恢复为 @prodata 的原始值。只有最后一个键会保留修改：

-- second iteration

SET @json=JSON_MODIFY(@ProData, '$.' + @ProKey + '.hasAnswer', CAST(1 as BIT))
-- you just overwrote your modifications with the value inside @prodata

解决办法是重新编排一下代码，可以在循环外初始化@json。