JSON_ARRAY_INSERT(json_doc, path, val[, path, val] ...)

Updates a JSON document, inserting into an array within the document
and returning the modified document. 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 or does not end with an array element
identifier.

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.

Pairs for which the path does not identify any array in the JSON
document are ignored. If a path identifies an array element, the
corresponding value is inserted at that element position, shifting any
following values to the right. If a path identifies an array position
past the end of an array, the value is inserted at the end of the
array.

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

