In SQL Server, the STRING_ESCAPE function is used to escape special characters in a string for certain formats, including JSON and XML. This function helps ensure that the output is valid and safe to use in these contexts by converting special characters into their escaped versions.
Using STRING_ESCAPE for JSON
To escape a string for JSON, you can use the STRING_ESCAPE function like this:
DECLARE @jsonString NVARCHAR(MAX) = 'This is a "sample" string with special characters: \n \t \ />';
SELECT STRING_ESCAPE(@jsonString, 'json') AS EscapedJsonString;
In this example:
- Special characters like quotes, backslashes, and control characters will be escaped properly for JSON.
- The second argument to STRING_ESCAPE specifies the format as 'json'.
Using STRING_ESCAPE for XML
To escape a string for XML, you can also use the STRING_ESCAPE function:
DECLARE @xmlString NVARCHAR(MAX) = 'This is a <sample> string with special characters: & < > "';
SELECT STRING_ESCAPE(@xmlString, 'xml') AS EscapedXmlString;
In this example:
- Special characters like <, >, &, and quotes will be escaped for XML.
- The second argument specifies the format as 'xml'.
Summary of Escape Characters
For JSON, the following characters are escaped:
- \" (double quote)
- \\ (backslash)
- \b (backspace)
- \f (form feed)
- \n (newline)
- \r (carriage return)
- \t (tab)
- Unicode characters can also be escaped.
For XML, the following characters are escaped:
- & (ampersand becomes &)
- < (less than becomes <)
- > (greater than becomes >)
- ' (single quote becomes ')
- " (double quote becomes ")
Important Notes
- STRING_ESCAPE is available starting from SQL Server 2016 (13.x).
- You should always properly escape strings when constructing JSON or XML to avoid errors and security issues such as injection attacks.
By using STRING_ESCAPE, you can confidently generate valid JSON and XML strings suitable for storage and transmission.