Error
Error Code:
3853
MySQL Error 3853: Invalid JSON Argument Type
Description
This error indicates that a MySQL function expecting a specific JSON data type has received an argument of an incompatible type. It commonly occurs when a string that is not valid JSON, or a non-string value, is passed to a JSON function that requires a properly formatted JSON input.
Error Message
Invalid JSON type in argument %u to function %s; an %s is required.
Known Causes
4 known causesNon-JSON String Argument
A function expecting a valid JSON string received a regular string that cannot be parsed as JSON.
Mismatched Argument Type
A non-string value (e.g., integer, boolean) was provided to a JSON function that specifically requires a JSON string or path.
Malformed JSON Syntax
The provided string intended to be JSON contains syntax errors, preventing MySQL from recognizing it as a valid JSON type.
Incorrect Function Usage
An argument was passed to a JSON function that expects a different JSON type or structure than what was provided.
Solutions
3 solutions available1. Ensure Correct Data Type for JSON Functions easy
Verify that the arguments passed to MySQL JSON functions are actually JSON strings or valid JSON types.
1
Review the function call that is triggering the error. Identify the specific argument causing the issue (indicated by `%u` in the error message).
2
Check the data type of the variable or column being passed to the function. If it's not a string, ensure it's cast or converted to a string that represents valid JSON.
SELECT JSON_EXTRACT(CAST(your_column AS CHAR), '$.your_key') FROM your_table;3
If you are constructing JSON dynamically, ensure that all values are correctly formatted as JSON types (e.g., strings are enclosed in double quotes, numbers are unquoted, booleans are `true` or `false`, null is `null`).
INSERT INTO your_table (json_column) VALUES ('{"name": "John Doe", "age": 30, "is_active": true, "address": null}');2. Correct Malformed JSON Strings medium
Identify and fix any JSON strings that do not adhere to the JSON standard.
1
Examine the data in the column or variable being used. Look for common JSON syntax errors such as missing or misplaced commas, incorrect quoting (single quotes instead of double quotes for keys and string values), unescaped special characters within strings, or invalid data types (e.g., using JavaScript `undefined` instead of `null`).
2
Use a JSON validator tool (online or a library in your programming language) to test the suspect JSON strings. This will help pinpoint specific syntax errors.
3
Update the malformed JSON strings in your database to correct syntax. This might involve manual updates or a script.
UPDATE your_table SET json_column = '{"corrected_key": "corrected_value"}' WHERE id = your_id;3. Handle NULL Values Gracefully easy
Ensure that your JSON operations correctly handle `NULL` values in the JSON data or as input.
1
When using JSON functions that expect specific types, be aware that passing `NULL` might be interpreted as an invalid argument type if the function expects a non-null JSON value.
2
Use the `IFNULL()` or `COALESCE()` function to provide a default valid JSON value (e.g., an empty JSON object `{}` or a specific default JSON structure) when a `NULL` is encountered, before passing it to a JSON function.
SELECT JSON_EXTRACT(IFNULL(your_column, '{}'), '$.your_key') FROM your_table;3
Alternatively, add checks in your application logic to ensure `NULL` values are handled appropriately before they reach the database or are processed by JSON functions.