If the length of results is greater then the value if the max_allowed_packet system variable then the String-valued functions will return NULL

The first position of a string (for those functions which operate on string), is numbered 1.

Non-integer arguments are rounded to the nearest integer (For functions that take length arguments).

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

CHAR() interprets all argument N as an integer and returns a string. NULL values are skipped.

mysql> SELECT CHAR(77,78);
+-------------+
| CHAR(77,78) |
+-------------+
| MN          |
+-------------+
1 row in set (0.00 sec)

mysql> SELECT CHAR(91,78,92,106);
+--------------------+
| CHAR(91,78,92,106) |
+--------------------+
| [N\j               |
+--------------------+
1 row in set (0.00 sec)

mysql> SELECT CHAR(97,78,92,106);
+--------------------+
| CHAR(97,78,92,106) |
+--------------------+
| aN\j               |
+--------------------+
1 row in set (0.00 sec)