Syntax:
JSON_EXTRACT(json_doc, path[, path] ...)

Returns data from a JSON document, selected from the parts of the
document matched by the path arguments. Returns NULL if any argument is
NULL or no paths locate a value in the document. An error occurs if the
json_doc argument is not a valid JSON document or any path argument is
not a valid path expression.

The return value consists of all values matched by the path arguments.
If it is possible that those arguments could return multiple values,
the matched values are autowrapped as an array, in the order
corresponding to the paths that produced them. Otherwise, the return
value is the single matched value.

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

