Question

JSON stored in a column 'DataJson' in table

[{
    "KickOffDate": "1-Jan-2019",
    "TeamSize": "11",
    "ClientEngineer": "Sagar",
    "WaitingPeriod": "16.5"
}]

Query

SELECT JSON_VALUE(DataJson,'$.KickOffDate') AS KickOffDate
     , JSON_VALUE(DataJson,'$.ClientEngineer') AS ClientEngineer
FROM [ABC].[Deliver]

Result

KickOffDate   ClientEngineer
NULL          NULL

Result should be:

KickOffDate   ClientEngineer
1-Jan-2019    Sagar

Answer 1

至少从SQL Server的JSON API的角度来看，您的JSON似乎格式错误。根据我的阅读，如果您的JSON数据由顶级JSON数组组成，则该数组需要有一个键名，并且所有内容都应包装在{ ... }中。

以下设置已经过测试并且可以正常工作：

WITH yourTable AS (
    SELECT '{ "data" : [{"KickOffDate": "1-Jan-2019", "TeamSize": "11", "ClientEngineer": "Sagar", "WaitingPeriod": "16.5"}] }' AS DataJson
)

SELECT
    JSON_VALUE(DataJson, '$.data[0].KickOffDate') AS KickOffDate,
    JSON_VALUE(DataJson, '$.data[0].ClientEngineer') AS ClientEngineer
FROM yourTable;

Demo

这是我使用的输入JSON的样子：

{
    "data" : [
        {
            "KickOffDate": "1-Jan-2019",
            "TeamSize": "11",
            "ClientEngineer": "Sagar",
            "WaitingPeriod": "16.5"
        }
    ]
}

Answer 2

您的sql查询错误。
您必须更正如下所示的查询。

 SELECT JSON_VALUE(DataJson,'$[0].KickOffDate') AS KickOffDate ,JSON_VALUE(DataJson,'$[0].ClientEngineer') AS ClientEngineer FROM [ABC].[Deliver]

表中存储的数据不是JSON对象，而是JSON数组。
因此，为了获取JSON Object的每个值，需要在JSON Array中设置JSON Object的索引。
否则，您可以将数据存储为JSON对象，然后查询就可以正常工作。

Answer 3

您有一个包含一个项目的JSON数组。假设您只对第一项感兴趣，则只需添加[0]：

SELECT JSON_VALUE(DataJson,'$[0].KickOffDate') AS KickOffDate
     , JSON_VALUE(DataJson,'$[0].ClientEngineer') AS ClientEngineer
FROM (
    SELECT '[{
            "KickOffDate": "1-Jan-2019",
            "TeamSize": "11",
            "ClientEngineer": "Sagar",
            "WaitingPeriod": "16.5"
        }]'
) AS t(DataJson)

如果要遍历所有项目，则需要使用OPENJSON：

SELECT KickOffDate, ClientEngineer
FROM (
    SELECT '[{
            "KickOffDate": "1-Jan-2019",
            "TeamSize": "11",
            "ClientEngineer": "Sagar",
            "WaitingPeriod": "16.5"
        }, {
            "KickOffDate": "1-Jan-2019",
            "TeamSize": "11",
            "ClientEngineer": "Sagar",
            "WaitingPeriod": "16.5"
        }, {
            "KickOffDate": "1-Jan-2019",
            "TeamSize": "11",
            "ClientEngineer": "Sagar",
            "WaitingPeriod": "16.5"
        }]'
) AS t(DataJson)
CROSS APPLY OPENJSON(DataJson)
WITH (
    KickOffDate    VARCHAR(100) '$.KickOffDate',
    ClientEngineer VARCHAR(100) '$.ClientEngineer'
)

Demo on db<>fiddle

SELECT JSON_VALUE From table returns null instead of value

3 个答案:

Demo