Syntax:
CHAR(N,... [USING charset_name])

CHAR() interprets each argument N as an integer and returns a string
consisting of the characters given by the code values of those
integers. NULL values are skipped.
CHAR() returns a string in the connection character set. As of MySQL
4.1.16, the optional USING clause may be used to produce a string in a
given character set:

mysql> SELECT CHARSET(CHAR(0x65)), CHARSET(CHAR(0x65 USING utf8));
+---------------------+--------------------------------+
| CHARSET(CHAR(0x65)) | CHARSET(CHAR(0x65 USING utf8)) |
+---------------------+--------------------------------+
| latin1              | utf8                           |
+---------------------+--------------------------------+
