MySQL has a hole in utf-8
Utf8 MySQL's actually not true UTF-8. utf8 only supports up to three bytes per character, while the real UTF-8 is up to four bytes per character.
MySQL has not fix this bug, they released a character set called utf8mb4 in 2010, bypassing the problem. Of course, they are not widely advertised to the new character set of (possibly because this bug so that they feel very embarrassed), so that now the network is still recommended that developers use utf8, but these proposals are wrong.
Summarized as follows:
(1) MySQL is utf8mb4 is the real UTF-8.
(2) MySQL is utf8 is a proprietary encoding that can encode Unicode characters is not much.