MySQL 5.7 Reference Manual
MySQL 5.7 Release Notes
Each character set has one or more collations, but each
collation is associated with one and only one character set.
Therefore, the following statement causes an error message
because the latin2_bin collation is not legal
with the latin1 character set:
mysql> SELECT _latin1 'x' COLLATE latin2_bin;
ERROR 1253 (42000): COLLATION 'latin2_bin' is not valid
for CHARACTER SET 'latin1'