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

Inserts data into 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 is ignored and
does not overwrite the existing document value. A path-value pair for a
nonexisting path in the document adds the value to the document if the
path identifies one of these types of values:

o A member not present in an existing object. The member is added to
  the object and associated with the new value.

o A position past the end of an existing array. The array is extended
  with the new value. If the existing value is not an array, it is
  autowrapped as an array, then extended with the new value.

Otherwise, 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: https://dev.mysql.com/doc/refman/5.7/en/json-modification-functions.html

