Syntax:
JSON_REPLACE(json_doc, path, val[, path, val] ...)

Replaces existing values in a JSON document and returns the result.
Returns NULL if any argument is NULL. An error occurs if the json_doc
argument is not a valid JSON document or any path argument is not a
valid path expression or contains a * or ** wildcard.

The path-value pairs are evaluated left to right. The document produced
by evaluating one pair becomes the new value against which the next
pair is evaluated.

A path-value pair for an existing path in the document overwrites the
existing document value with the new value. A path-value pair for a
nonexisting path in the document is ignored and has no effect.

For a comparison of JSON_INSERT(), JSON_REPLACE(), and JSON_SET(), see
the discussion of JSON_SET().

URL: http://dev.mysql.com/doc/refman/5.7/en/json-modification-functions.html

