Hvis du bruger JSON_VALUE() for at returnere værdier, der består af en lang streng, kan du opleve, at den returnerer NULL i stedet for den faktiske værdi.
Eller du får muligvis en fejl.
Årsagen
Dette problem opstår, fordi JSON_VALUE() returnerer en enkelt tekstværdi af typen nvarchar(4000) .
Når du bruger JSON_VALUE() for at returnere strenge længere end 4000 tegn, får du enten en fejl eller en NULL værdi, afhængigt af den stitilstand, du bruger.
Laks tilstand vs streng tilstand
Om du får en fejl eller NULL vil afhænge af, om du bruger lax eller strict tilstand.
Når værdien er større end 4000 tegn:
- I
laxtilstand,JSON_VALUE()returnerer null. - I
stricttilstand,JSON_VALUE()returnerer en fejl.
Eksempel på problemet
Her er et eksempel på kode, der forårsager problemet.
Lad os tage to eksempler; en i lax tilstand, og den anden i strict tilstand.
Laks tilstand
DECLARE @json nvarchar(max) = N'{
"article" : {
"id" : 1,
"text" : "If you have to return scalar values greater than 4000 characters, use the OPENJSON function instead of JSON_VALUE. This text contains more than 4000 characters, which will cause issues for the JSON_VALUE function in SQL Server. This is because the JSON_VALUE function returns a single text value of type nvarchar(4000). If the value is greater than 4000 characters: In lax mode, JSON_VALUE returns null. In strict mode, JSON_VALUE returns an error. If you have to return scalar values greater than 4000 characters, use the OPENJSON function instead of JSON_VALUE. This text contains more than 4000 characters, which will cause issues for the JSON_VALUE function in SQL Server. This is because the JSON_VALUE function returns a single text value of type nvarchar(4000). If the value is greater than 4000 characters: In lax mode, JSON_VALUE returns null. In strict mode, JSON_VALUE returns an error. If you have to return scalar values greater than 4000 characters, use the OPENJSON function instead of JSON_VALUE. This text contains more than 4000 characters, which will cause issues for the JSON_VALUE function in SQL Server. This is because the JSON_VALUE function returns a single text value of type nvarchar(4000). If the value is greater than 4000 characters: In lax mode, JSON_VALUE returns null. In strict mode, JSON_VALUE returns an error. If you have to return scalar values greater than 4000 characters, use the OPENJSON function instead of JSON_VALUE. This text contains more than 4000 characters, which will cause issues for the JSON_VALUE function in SQL Server. This is because the JSON_VALUE function returns a single text value of type nvarchar(4000). If the value is greater than 4000 characters: In lax mode, JSON_VALUE returns null. In strict mode, JSON_VALUE returns an error. If you have to return scalar values greater than 4000 characters, use the OPENJSON function instead of JSON_VALUE. This text contains more than 4000 characters, which will cause issues for the JSON_VALUE function in SQL Server. This is because the JSON_VALUE function returns a single text value of type nvarchar(4000). If the value is greater than 4000 characters: In lax mode, JSON_VALUE returns null. In strict mode, JSON_VALUE returns an error. If you have to return scalar values greater than 4000 characters, use the OPENJSON function instead of JSON_VALUE. This text contains more than 4000 characters, which will cause issues for the JSON_VALUE function in SQL Server. This is because the JSON_VALUE function returns a single text value of type nvarchar(4000). If the value is greater than 4000 characters: In lax mode, JSON_VALUE returns null. In strict mode, JSON_VALUE returns an error. If you have to return scalar values greater than 4000 characters, use the OPENJSON function instead of JSON_VALUE. This text contains more than 4000 characters, which will cause issues for the JSON_VALUE function in SQL Server. This is because the JSON_VALUE function returns a single text value of type nvarchar(4000). If the value is greater than 4000 characters: In lax mode, JSON_VALUE returns null. In strict mode, JSON_VALUE returns an error. If you have to return scalar values greater than 4000 characters, use the OPENJSON function instead of JSON_VALUE. This text contains more than 4000 characters, which will cause issues for the JSON_VALUE function in SQL Server. This is because the JSON_VALUE function returns a single text value of type nvarchar(4000). If the value is greater than 4000 characters: In lax mode, JSON_VALUE returns null. In strict mode, JSON_VALUE returns an error. If you have to return scalar values greater than 4000 characters, use the OPENJSON function instead of JSON_VALUE. This text contains more than 4000 characters, which will cause issues for the JSON_VALUE function in SQL Server. This is because the JSON_VALUE function returns a single text value of type nvarchar(4000). If the value is greater than 4000 characters: In lax mode, JSON_VALUE returns null. In strict mode, JSON_VALUE returns an error."
}
}';
SELECT JSON_VALUE(@json, 'lax $.article.text');Resultat:
+--------------------+ | (No column name) | |--------------------| | NULL | +--------------------+
Som nævnt i lax tilstand returnerer den NULL .
Strikt tilstand
DECLARE @json nvarchar(max) = N'{
"article" : {
"id" : 1,
"text" : "If you have to return scalar values greater than 4000 characters, use the OPENJSON function instead of JSON_VALUE. This text contains more than 4000 characters, which will cause issues for the JSON_VALUE function in SQL Server. This is because the JSON_VALUE function returns a single text value of type nvarchar(4000). If the value is greater than 4000 characters: In lax mode, JSON_VALUE returns null. In strict mode, JSON_VALUE returns an error. If you have to return scalar values greater than 4000 characters, use the OPENJSON function instead of JSON_VALUE. This text contains more than 4000 characters, which will cause issues for the JSON_VALUE function in SQL Server. This is because the JSON_VALUE function returns a single text value of type nvarchar(4000). If the value is greater than 4000 characters: In lax mode, JSON_VALUE returns null. In strict mode, JSON_VALUE returns an error. If you have to return scalar values greater than 4000 characters, use the OPENJSON function instead of JSON_VALUE. This text contains more than 4000 characters, which will cause issues for the JSON_VALUE function in SQL Server. This is because the JSON_VALUE function returns a single text value of type nvarchar(4000). If the value is greater than 4000 characters: In lax mode, JSON_VALUE returns null. In strict mode, JSON_VALUE returns an error. If you have to return scalar values greater than 4000 characters, use the OPENJSON function instead of JSON_VALUE. This text contains more than 4000 characters, which will cause issues for the JSON_VALUE function in SQL Server. This is because the JSON_VALUE function returns a single text value of type nvarchar(4000). If the value is greater than 4000 characters: In lax mode, JSON_VALUE returns null. In strict mode, JSON_VALUE returns an error. If you have to return scalar values greater than 4000 characters, use the OPENJSON function instead of JSON_VALUE. This text contains more than 4000 characters, which will cause issues for the JSON_VALUE function in SQL Server. This is because the JSON_VALUE function returns a single text value of type nvarchar(4000). If the value is greater than 4000 characters: In lax mode, JSON_VALUE returns null. In strict mode, JSON_VALUE returns an error. If you have to return scalar values greater than 4000 characters, use the OPENJSON function instead of JSON_VALUE. This text contains more than 4000 characters, which will cause issues for the JSON_VALUE function in SQL Server. This is because the JSON_VALUE function returns a single text value of type nvarchar(4000). If the value is greater than 4000 characters: In lax mode, JSON_VALUE returns null. In strict mode, JSON_VALUE returns an error. If you have to return scalar values greater than 4000 characters, use the OPENJSON function instead of JSON_VALUE. This text contains more than 4000 characters, which will cause issues for the JSON_VALUE function in SQL Server. This is because the JSON_VALUE function returns a single text value of type nvarchar(4000). If the value is greater than 4000 characters: In lax mode, JSON_VALUE returns null. In strict mode, JSON_VALUE returns an error. If you have to return scalar values greater than 4000 characters, use the OPENJSON function instead of JSON_VALUE. This text contains more than 4000 characters, which will cause issues for the JSON_VALUE function in SQL Server. This is because the JSON_VALUE function returns a single text value of type nvarchar(4000). If the value is greater than 4000 characters: In lax mode, JSON_VALUE returns null. In strict mode, JSON_VALUE returns an error. If you have to return scalar values greater than 4000 characters, use the OPENJSON function instead of JSON_VALUE. This text contains more than 4000 characters, which will cause issues for the JSON_VALUE function in SQL Server. This is because the JSON_VALUE function returns a single text value of type nvarchar(4000). If the value is greater than 4000 characters: In lax mode, JSON_VALUE returns null. In strict mode, JSON_VALUE returns an error."
}
}';
SELECT JSON_VALUE(@json, 'strict $.article.text');Resultat:
Msg 13625, Level 16, State 1, Line 7 String value in the specified JSON path would be truncated.
Som forventet får vi en fejl. Heldigvis giver fejlen et fingerpeg om, hvad der gik galt, da den nævner, at strengværdien ville blive afkortet.
Løsning
Heldigvis er OPENJSON() Funktionen har ikke den samme begrænsning på 4000 tegn som JSON_VALUE() har på sin returværdi.
OPENJSON() returnerer JSON-værdier som en nvarchar(max) .
Derfor kan vi bruge følgende kode til at løse problemet.
DECLARE @json nvarchar(max) = N'{
"article" : {
"id" : 1,
"text" : "If you have to return scalar values greater than 4000 characters, use the OPENJSON function instead of JSON_VALUE. This text contains more than 4000 characters, which will cause issues for the JSON_VALUE function in SQL Server. This is because the JSON_VALUE function returns a single text value of type nvarchar(4000). If the value is greater than 4000 characters: In lax mode, JSON_VALUE returns null. In strict mode, JSON_VALUE returns an error. If you have to return scalar values greater than 4000 characters, use the OPENJSON function instead of JSON_VALUE. This text contains more than 4000 characters, which will cause issues for the JSON_VALUE function in SQL Server. This is because the JSON_VALUE function returns a single text value of type nvarchar(4000). If the value is greater than 4000 characters: In lax mode, JSON_VALUE returns null. In strict mode, JSON_VALUE returns an error. If you have to return scalar values greater than 4000 characters, use the OPENJSON function instead of JSON_VALUE. This text contains more than 4000 characters, which will cause issues for the JSON_VALUE function in SQL Server. This is because the JSON_VALUE function returns a single text value of type nvarchar(4000). If the value is greater than 4000 characters: In lax mode, JSON_VALUE returns null. In strict mode, JSON_VALUE returns an error. If you have to return scalar values greater than 4000 characters, use the OPENJSON function instead of JSON_VALUE. This text contains more than 4000 characters, which will cause issues for the JSON_VALUE function in SQL Server. This is because the JSON_VALUE function returns a single text value of type nvarchar(4000). If the value is greater than 4000 characters: In lax mode, JSON_VALUE returns null. In strict mode, JSON_VALUE returns an error. If you have to return scalar values greater than 4000 characters, use the OPENJSON function instead of JSON_VALUE. This text contains more than 4000 characters, which will cause issues for the JSON_VALUE function in SQL Server. This is because the JSON_VALUE function returns a single text value of type nvarchar(4000). If the value is greater than 4000 characters: In lax mode, JSON_VALUE returns null. In strict mode, JSON_VALUE returns an error. If you have to return scalar values greater than 4000 characters, use the OPENJSON function instead of JSON_VALUE. This text contains more than 4000 characters, which will cause issues for the JSON_VALUE function in SQL Server. This is because the JSON_VALUE function returns a single text value of type nvarchar(4000). If the value is greater than 4000 characters: In lax mode, JSON_VALUE returns null. In strict mode, JSON_VALUE returns an error. If you have to return scalar values greater than 4000 characters, use the OPENJSON function instead of JSON_VALUE. This text contains more than 4000 characters, which will cause issues for the JSON_VALUE function in SQL Server. This is because the JSON_VALUE function returns a single text value of type nvarchar(4000). If the value is greater than 4000 characters: In lax mode, JSON_VALUE returns null. In strict mode, JSON_VALUE returns an error. If you have to return scalar values greater than 4000 characters, use the OPENJSON function instead of JSON_VALUE. This text contains more than 4000 characters, which will cause issues for the JSON_VALUE function in SQL Server. This is because the JSON_VALUE function returns a single text value of type nvarchar(4000). If the value is greater than 4000 characters: In lax mode, JSON_VALUE returns null. In strict mode, JSON_VALUE returns an error. If you have to return scalar values greater than 4000 characters, use the OPENJSON function instead of JSON_VALUE. This text contains more than 4000 characters, which will cause issues for the JSON_VALUE function in SQL Server. This is because the JSON_VALUE function returns a single text value of type nvarchar(4000). If the value is greater than 4000 characters: In lax mode, JSON_VALUE returns null. In strict mode, JSON_VALUE returns an error."
}
}';
SELECT text FROM OPENJSON(@json, '$.article')
WITH (text nvarchar(max) '$.text');Resultat:
If you have to return scalar values greater than 4000 characters, use the OPENJSON function instead of JSON_VALUE. This text contains more than 4000 characters, which will cause issues for the JSON_VALUE function in SQL Server. This is because the JSON_VALUE function returns a single text value of type nvarchar(4000). If the value is greater than 4000 characters: In lax mode, JSON_VALUE returns null. In strict mode, JSON_VALUE returns an error. If you have to return scalar values greater than 4000 characters, use the OPENJSON function instead of JSON_VALUE. This text contains more than 4000 characters, which will cause issues for the JSON_VALUE function in SQL Server. This is because the JSON_VALUE function returns a single text value of type nvarchar(4000). If the value is greater than 4000 characters: In lax mode, JSON_VALUE returns null. In strict mode, JSON_VALUE returns an error. If you have to return scalar values greater than 4000 characters, use the OPENJSON function instead of JSON_VALUE. This text contains more than 4000 characters, which will cause issues for the JSON_VALUE function in SQL Server. This is because the JSON_VALUE function returns a single text value of type nvarchar(4000). If the value is greater than 4000 characters: In lax mode, JSON_VALUE returns null. In strict mode, JSON_VALUE returns an error. If you have to return scalar values greater than 4000 characters, use the OPENJSON function instead of JSON_VALUE. This text contains more than 4000 characters, which will cause issues for the JSON_VALUE function in SQL Server. This is because the JSON_VALUE function returns a single text value of type nvarchar(4000). If the value is greater than 4000 characters: In lax mode, JSON_VALUE returns null. In strict mode, JSON_VALUE returns an error. If you have to return scalar values greater than 4000 characters, use the OPENJSON function instead of JSON_VALUE. This text contains more than 4000 characters, which will cause issues for the JSON_VALUE function in SQL Server. This is because the JSON_VALUE function returns a single text value of type nvarchar(4000). If the value is greater than 4000 characters: In lax mode, JSON_VALUE returns null. In strict mode, JSON_VALUE returns an error. If you have to return scalar values greater than 4000 characters, use the OPENJSON function instead of JSON_VALUE. This text contains more than 4000 characters, which will cause issues for the JSON_VALUE function in SQL Server. This is because the JSON_VALUE function returns a single text value of type nvarchar(4000). If the value is greater than 4000 characters: In lax mode, JSON_VALUE returns null. In strict mode, JSON_VALUE returns an error. If you have to return scalar values greater than 4000 characters, use the OPENJSON function instead of JSON_VALUE. This text contains more than 4000 characters, which will cause issues for the JSON_VALUE function in SQL Server. This is because the JSON_VALUE function returns a single text value of type nvarchar(4000). If the value is greater than 4000 characters: In lax mode, JSON_VALUE returns null. In strict mode, JSON_VALUE returns an error. If you have to return scalar values greater than 4000 characters, use the OPENJSON function instead of JSON_VALUE. This text contains more than 4000 characters, which will cause issues for the JSON_VALUE function in SQL Server. This is because the JSON_VALUE function returns a single text value of type nvarchar(4000). If the value is greater than 4000 characters: In lax mode, JSON_VALUE returns null. In strict mode, JSON_VALUE returns an error. If you have to return scalar values greater than 4000 characters, use the OPENJSON function instead of JSON_VALUE. This text contains more than 4000 characters, which will cause issues for the JSON_VALUE function in SQL Server. This is because the JSON_VALUE function returns a single text value of type nvarchar(4000). If the value is greater than 4000 characters: In lax mode, JSON_VALUE returns null. In strict mode, JSON_VALUE returns an error.