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How FOR JSON escapes special characters and control characters

Applies to: SQL Server 2016 (13.x) and later versions Azure SQL Database Azure SQL Managed Instance Azure Synapse Analytics (serverless SQL pool only) SQL analytics endpoint in Microsoft Fabric Warehouse in Microsoft Fabric SQL database in Microsoft Fabric Preview

This article describes how the FOR JSON clause of a SQL Server SELECT statement escapes special characters and represents control characters in the JSON output.

This article describes the built-in support for JSON in Microsoft SQL Server. For general information about escaping and encoding in JSON, see Section 2.5 of the JSON RFC.

Escape of special characters

If the source data contains special characters, the FOR JSON clause escapes them in the JSON output with \, as shown in the following table. This escaping occurs both in the names of properties and in their values.

Special character Escaped output
Quotation mark (") \"
Backslash (\) \\
Slash (/) \/
Backspace \b
Form feed \f
New line \n
Carriage return \r
Horizontal tab \t

Control characters

If the source data contains control characters, the FOR JSON clause encodes them in the JSON output in \u<code> format, as shown in the following table.

Control character Encoded output
CHAR(0) \u0000
CHAR(1) \u0001
... ...
CHAR(31) \u001f

Example

Here's an example of the FOR JSON output for source data that includes both special characters and control characters.

Query:

SELECT 'VALUE\    /
  "' AS [KEY\/"],
    CHAR(0) AS '0',
    CHAR(1) AS '1',
    CHAR(31) AS '31'
FOR JSON PATH;

Result:

[
    {
        "KEY\\\/\"": "VALUE\\    \/\r\n  \"",
        "0": "\u0000",
        "1": "\u0001",
        "31": "\u001f"
    }
]

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