如何從JSON字符串讀取長整型值的屬性？

Question

我有一個JSON對象，其中一個屬性的值很長。當我嘗試使用JSON_VALUE()提取此值時，它將返回null。

declare @json nvarchar(max) = 
' 
{ 
    "AVeryLongValue": "Founded in 2008, Stack Overflow is the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. More than 50 million professional and aspiring programmers visit Stack Overflow each month to help solve coding problems, develop new skills, and find job opportunities. Stack Overflow partners with businesses to help them understand, hire, engage, and enable the worlds developers. Our products and services are focused on developer marketing, technical recruiting, market research, and enterprise knowledge sharing. Learn more about our business solutions here. Founded in 2008, Stack Overflow is the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. More than 50 million professional and aspiring programmers visit Stack Overflow each month to help solve coding problems, develop new skills, and find job opportunities. Stack Overflow partners with businesses to help them understand, hire, engage, and enable the worlds developers. Our products and services are focused on developer marketing, technical recruiting, market research, and enterprise knowledge sharing. Learn more about our business solutions here. Founded in 2008, Stack Overflow is the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. More than 50 million professional and aspiring programmers visit Stack Overflow each month to help solve coding problems, develop new skills, and find job opportunities. Stack Overflow partners with businesses to help them understand, hire, engage, and enable the worlds developers. Our products and services are focused on developer marketing, technical recruiting, market research, and enterprise knowledge sharing. Learn more about our business solutions here. Founded in 2008, Stack Overflow is the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. More than 50 million professional and aspiring programmers visit Stack Overflow each month to help solve coding problems, develop new skills, and find job opportunities. Stack Overflow partners with businesses to help them understand, hire, engage, and enable the worlds developers. Our products and services are focused on developer marketing, technical recruiting, market research, and enterprise knowledge sharing. Learn more about our business solutions here. Founded in 2008, Stack Overflow is the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. More than 50 million professional and aspiring programmers visit Stack Overflow each month to help solve coding problems, develop new skills, and find job opportunities. Stack Overflow partners with businesses to help them understand, hire, engage, and enable the worlds developers. Our products and services are focused on developer marketing, technical recruiting, market research, and enterprise knowledge sharing. Learn more about our business solutions here. Founded in 2008, Stack Overflow is the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. More than 50 million professional and aspiring programmers visit Stack Overflow each month to help solve coding problems, develop new skills, and find job opportunities. Stack Overflow partners with businesses to help them understand, hire, engage, and enable the worlds developers. Our products and services are focused on developer marketing, technical recruiting, market research, and enterprise knowledge sharing. Learn more about our business solutions here. Founded in 2008, Stack Overflow is the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. More than 50 million professional and aspiring programmers visit Stack Overflow each month to help solve coding problems, develop new skills, and find job opportunities. Stack Overflow partners with businesses to help them understand, hire, engage, and enable the worlds developers. Our products and services are focused on developer marketing, technical recruiting, market research, and enterprise knowledge sharing. Learn more about our business solutions here. Founded in 2008, Stack Overflow is the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. More than 50 million professional and aspiring programmers visit Stack Overflow each month to help solve coding problems, develop new skills, and find job opportunities. Stack Overflow partners with businesses to help them understand, hire, engage, and enable the worlds developers. Our products and services are focused on developer marketing, technical recruiting, market research, and enterprise knowledge sharing. Learn more about our business solutions here." 
} 
' 
select json_value(@json, '$.AVeryLongValue') as 'AVeryLongValue' 

結果：

AVeryLongValue 
-------- 
NULL 

我使用is_json(@json)確認後，JSON是有效的。長的值似乎沒有任何特殊字符等。

如果我縮短了值，我確實得到了我想要的值，所以代碼似乎沒問題。例如：

declare @json nvarchar(max) = ' 
{ 
    "AVeryLongValue": "Founded in 2008" 
} 
' 
select json_value(@json, '$.AVeryLongValue') as 'AVeryLongValue' 

結果：

AVeryLongValue 
------------ 
Founded in 2008 

問題：

1. 讀取long值時，爲什麼我得到一個空？它是否需要特殊處理？
2. 我有這個屬性的長和短值的JSON對象的組合。此外，有時該屬性完全丟失，因此對於這些對象，JSON_VALUE（）將返回null。任何建議如何應用條件特殊處理僅適用於該屬性爲long值的對象？

Answer 1

爲什麼在讀取長值時會出現空值？

因爲該值超過4000個字符並且json_value()無法處理它。這裏是MSDN reference

返回值

返回類型爲nvarchar（4000）的一個單一的文本值。

如果該值大於4000個字符：

In lax mode, JSON_VALUE returns null. 

In strict mode, JSON_VALUE returns an error. 

是否需要任何特殊處理？我如何解決這個限制？

在15:00發現這個偉大的視頻SQL Server 2016 and JSON Support on Channel9，其中提到了這個問題，並建議在25:00

select value from openjson(@json) where[key] = 'AVeryLongValue' 

一種變通方法我有JSON的混合與此多空值的對象屬性。此外，有時該屬性完全丟失，因此對於這些對象，JSON_VALUE（）將返回null。任何建議如何應用條件特殊處理僅適用於該屬性爲long值的對象？

在提供給json_value()的JSON表達，使用'strict' path mode可以使json_value()到如果屬性值是長和將被截斷引發錯誤。

declare @json nvarchar(max) = 
' 
{ 
    "AVeryLongValue": "Founded in 2008, Stack Overflow is the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. More than 50 million professional and aspiring programmers visit Stack Overflow each month to help solve coding problems, develop new skills, and find job opportunities. Stack Overflow partners with businesses to help them understand, hire, engage, and enable the worlds developers. Our products and services are focused on developer marketing, technical recruiting, market research, and enterprise knowledge sharing. Learn more about our business solutions here. Founded in 2008, Stack Overflow is the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. More than 50 million professional and aspiring programmers visit Stack Overflow each month to help solve coding problems, develop new skills, and find job opportunities. Stack Overflow partners with businesses to help them understand, hire, engage, and enable the worlds developers. Our products and services are focused on developer marketing, technical recruiting, market research, and enterprise knowledge sharing. Learn more about our business solutions here. Founded in 2008, Stack Overflow is the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. More than 50 million professional and aspiring programmers visit Stack Overflow each month to help solve coding problems, develop new skills, and find job opportunities. Stack Overflow partners with businesses to help them understand, hire, engage, and enable the worlds developers. Our products and services are focused on developer marketing, technical recruiting, market research, and enterprise knowledge sharing. Learn more about our business solutions here. Founded in 2008, Stack Overflow is the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. More than 50 million professional and aspiring programmers visit Stack Overflow each month to help solve coding problems, develop new skills, and find job opportunities. Stack Overflow partners with businesses to help them understand, hire, engage, and enable the worlds developers. Our products and services are focused on developer marketing, technical recruiting, market research, and enterprise knowledge sharing. Learn more about our business solutions here. Founded in 2008, Stack Overflow is the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. More than 50 million professional and aspiring programmers visit Stack Overflow each month to help solve coding problems, develop new skills, and find job opportunities. Stack Overflow partners with businesses to help them understand, hire, engage, and enable the worlds developers. Our products and services are focused on developer marketing, technical recruiting, market research, and enterprise knowledge sharing. Learn more about our business solutions here. Founded in 2008, Stack Overflow is the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. More than 50 million professional and aspiring programmers visit Stack Overflow each month to help solve coding problems, develop new skills, and find job opportunities. Stack Overflow partners with businesses to help them understand, hire, engage, and enable the worlds developers. Our products and services are focused on developer marketing, technical recruiting, market research, and enterprise knowledge sharing. Learn more about our business solutions here. Founded in 2008, Stack Overflow is the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. More than 50 million professional and aspiring programmers visit Stack Overflow each month to help solve coding problems, develop new skills, and find job opportunities. Stack Overflow partners with businesses to help them understand, hire, engage, and enable the worlds developers. Our products and services are focused on developer marketing, technical recruiting, market research, and enterprise knowledge sharing. Learn more about our business solutions here. Founded in 2008, Stack Overflow is the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. More than 50 million professional and aspiring programmers visit Stack Overflow each month to help solve coding problems, develop new skills, and find job opportunities. Stack Overflow partners with businesses to help them understand, hire, engage, and enable the worlds developers. Our products and services are focused on developer marketing, technical recruiting, market research, and enterprise knowledge sharing. Learn more about our business solutions here." 
} 
' 
declare @AVeryLongValue nvarchar(max) 
select @AVeryLongValue = json_value(@json, 'strict $.AVeryLongValue') 

成果轉化

Msg 13625, Level 16, State 1, Line 13 
String value in the specified JSON path would be truncated. 

此外，如果物業從JSON丟失，這將導致如下錯誤：

Msg 13608, Level 16, State 5, Line 12 
Property cannot be found on the specified JSON path. 

我可以使用strict模式try-catch沿像這樣的邏輯來處理對象的混合。

declare @json nvarchar(max) = 
' 
{ 
    "AVeryLongValue": "Founded in 2008, Stack Overflow is the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. More than 50 million professional and aspiring programmers visit Stack Overflow each month to help solve coding problems, develop new skills, and find job opportunities. Stack Overflow partners with businesses to help them understand, hire, engage, and enable the worlds developers. Our products and services are focused on developer marketing, technical recruiting, market research, and enterprise knowledge sharing. Learn more about our business solutions here. Founded in 2008, Stack Overflow is the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. More than 50 million professional and aspiring programmers visit Stack Overflow each month to help solve coding problems, develop new skills, and find job opportunities. Stack Overflow partners with businesses to help them understand, hire, engage, and enable the worlds developers. Our products and services are focused on developer marketing, technical recruiting, market research, and enterprise knowledge sharing. Learn more about our business solutions here. Founded in 2008, Stack Overflow is the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. More than 50 million professional and aspiring programmers visit Stack Overflow each month to help solve coding problems, develop new skills, and find job opportunities. Stack Overflow partners with businesses to help them understand, hire, engage, and enable the worlds developers. Our products and services are focused on developer marketing, technical recruiting, market research, and enterprise knowledge sharing. Learn more about our business solutions here. Founded in 2008, Stack Overflow is the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. More than 50 million professional and aspiring programmers visit Stack Overflow each month to help solve coding problems, develop new skills, and find job opportunities. Stack Overflow partners with businesses to help them understand, hire, engage, and enable the worlds developers. Our products and services are focused on developer marketing, technical recruiting, market research, and enterprise knowledge sharing. Learn more about our business solutions here. Founded in 2008, Stack Overflow is the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. More than 50 million professional and aspiring programmers visit Stack Overflow each month to help solve coding problems, develop new skills, and find job opportunities. Stack Overflow partners with businesses to help them understand, hire, engage, and enable the worlds developers. Our products and services are focused on developer marketing, technical recruiting, market research, and enterprise knowledge sharing. Learn more about our business solutions here. Founded in 2008, Stack Overflow is the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. More than 50 million professional and aspiring programmers visit Stack Overflow each month to help solve coding problems, develop new skills, and find job opportunities. Stack Overflow partners with businesses to help them understand, hire, engage, and enable the worlds developers. Our products and services are focused on developer marketing, technical recruiting, market research, and enterprise knowledge sharing. Learn more about our business solutions here. Founded in 2008, Stack Overflow is the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. More than 50 million professional and aspiring programmers visit Stack Overflow each month to help solve coding problems, develop new skills, and find job opportunities. Stack Overflow partners with businesses to help them understand, hire, engage, and enable the worlds developers. Our products and services are focused on developer marketing, technical recruiting, market research, and enterprise knowledge sharing. Learn more about our business solutions here. Founded in 2008, Stack Overflow is the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. More than 50 million professional and aspiring programmers visit Stack Overflow each month to help solve coding problems, develop new skills, and find job opportunities. Stack Overflow partners with businesses to help them understand, hire, engage, and enable the worlds developers. Our products and services are focused on developer marketing, technical recruiting, market research, and enterprise knowledge sharing. Learn more about our business solutions here." 
} 
' 

declare @AVeryLongValue nvarchar(max) 
begin try 
    select @AVeryLongValue = json_value(@json, 'strict $.AVeryLongValue') 
end try 
begin catch 
    select 'In catch section' 
    select @AVeryLongValue = value from openjson(@json) where[key] = 'AVeryLongValue' 
end catch 
if @AVeryLongValue is null 
    select 'The JSON did not have property AVeryLongValue' 
else 
    select @AVeryLongValue 

Answer 2

我可能找到了一種方法來管理比JSON_Value nvarchar (4000)更大的值。

使用WITH子句：

DECLARE @jsonInfo NVARCHAR(MAX) 
SET @jsonInfo=N'{ 
    "Items": [ { 
      "guid": "f0acb160-62eb-4622-bef2-bb9e8afe7314", 
      "timestamp": "2017-10-31T23:59:51.093Z", 
      "data": { 
       "LongText": "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Maecenas venenatis vel orci a tincidunt. Maecenas suscipit sed neque non mollis. Proin nec mollis lacus, in gravida lorem. Nullam pharetra urna vitae consectetur placerat. Proin rutrum risus vitae nunc mattis, nec pellentesque ligula viverra. Maecenas at semper libero. Curabitur porta urna vel arcu interdum scelerisque. Cras ultrices tincidunt pulvinar. Nam molestie aliquet sapien nec ultricies. Nulla facilisis quam a ante lobortis tincidunt. Morbi ac nulla mi.Morbi mattis in ex non ullamcorper. Etiam sit amet lacus eros. Suspendisse ac magna purus. Quisque vel lectus a libero posuere condimentum ac posuere orci. Fusce vel molestie velit. Nunc vulputate mauris consequat massa imperdiet, in aliquet metus dignissim. Donec posuere odio suscipit, sollicitudin tellus nec, ultricies augue. Duis vel lacinia massa. Nam venenatis mauris ut risus pharetra bibendum. Phasellus ornare enim eu enim mattis efficitur. Cras in arcu leo. Maecenas nec tempus mauris. Nulla vel tortor non elit elementum maximus. Nulla eu ex neque. Duis nisi odio, finibus a dui vel, sodales venenatis leo. Pellentesque fermentum rutrum pellentesque.Nullam euismod nulla lectus, a blandit nisi viverra non. Aliquam ut auctor turpis. Orci varius natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. Vestibulum id ante scelerisque, aliquet ipsum interdum, dapibus diam. Fusce faucibus orci ut eros aliquet finibus. Maecenas magna turpis, pulvinar a eleifend sed, gravida eget massa. Praesent laoreet convallis condimentum. Aenean rutrum leo id malesuada fermentum. Nullam quis ullamcorper ipsum, non imperdiet mi. Cras ex neque, molestie maximus rutrum sit amet, rhoncus quis justo. Cras venenatis consequat justo sed cursus. Phasellus mollis malesuada interdum. Aliquam erat volutpat. Curabitur ultricies dapibus ante sit amet convallis.Quisque massa mi, mattis sed semper eu, rutrum ut massa. Nam velit enim, placerat id placerat et, aliquam vel purus. Nulla non auctor eros. Nullam sed elit metus. Donec tempor tempus sagittis. Vestibulum ante ipsum primis in faucibus orci luctus et ultrices posuere cubilia Curae; Nunc elementum gravida auctor. Aenean posuere pretium consequat.Orci varius natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. In eu finibus ligula, a blandit felis. Cras interdum sapien ac urna fringilla ornare. In consequat lectus luctus tellus tempus pellentesque. Duis vitae turpis tincidunt, tincidunt mauris at, vehicula ligula. Curabitur sed tortor lacinia sapien varius tincidunt vitae nec est. Duis pulvinar eros lorem, id luctus justo convallis tempor. Pellentesque sit amet eros a magna condimentum hendrerit non vitae enim.Pellentesque sit amet ex vel felis auctor luctus ultricies ac mauris. Vivamus tempus sit amet ipsum vitae hendrerit. Vivamus dignissim blandit magna tempor pharetra. Class aptent taciti sociosqu ad litora torquent per conubia nostra, per inceptos himenaeos. Vestibulum ante ipsum primis in faucibus orci luctus et ultrices posuere cubilia Curae; Nam tempus tristique justo egestas tempor. Nulla lacus tortor, interdum ac ante pulvinar, ultricies mollis ligula. Donec facilisis blandit justo, ac vulputate urna tempor vel. Curabitur commodo ex et fringilla pellentesque. Donec lobortis lorem vel ante rhoncus posuere. Suspendisse cursus velit sit amet nisi sagittis tristique. Ut nec accumsan risus, id tincidunt ipsum. Vivamus convallis sodales tellus vel ultricies.Nam semper risus ligula, eu venenatis ipsum fringilla quis. Sed cursus pellentesque ex eu finibus. Morbi ligula lectus, semper et laoreet id, porttitor quis sapien. Class aptent taciti sociosqu ad litora torquent per conubia nostra, per inceptos himenaeos. Nulla a feugiat est, vel faucibus arcu. Vivamus molestie tortor a augue maximus vulputate. Aliquam at nulla nibh. Nullam blandit quam sed tortor gravida, nec scelerisque felis interdum.Cras et interdum elit, quis laoreet sapien. Integer arcu dui, interdum eu egestas placerat, posuere a posuere." 
      } 
     } 
    ] 
}' 

-- doesnt work because of the JSON_Value nvarchar (4000) 
SELECT 
JSON_Value (i.value, '$.guid') as [GUID], 
    CONVERT(datetime, JSON_Value (i.value, '$.timestamp')) as [TimeStamp], 
    JSON_Value (i.value, '$.data.LongText') as LongText 
FROM OPENJSON (@jsonInfo, '$.Items') as i 

-- workaround 
select 
i.* 
FROM OPENJSON (@jsonInfo, '$.Items') 
WITH ([GUID] nvarchar(40) '$.guid' , 
    [TimeStamp] Datetime '$.timestamp', 
     LongText nvarchar(MAX) '$.data.LongText' 
) as i 

默認情況下，我認爲這是最好使用WITH條款，在SQL Server上的博客，據說它有更好的性能。 Blog Post