MySQL stored procedure reported illegal mix of collations

I wrote a stored procedure with a cursor in it, and then traversed the cursor to update the value of the other table based on the result of the traversal, which is the general case;

The problem was reported at update: illegal mix of collations (utf8_unicode_ci,implicit) and (utf8_general_ci,implicit) error.

Table and field collate are UTF8_UNICODE_CI, but the server is utf8_general_ci, still can't change!

There is no way to convert only in stored procedures!

Workaround : Converts the comparison equation to a string, such as " CONVERT (variable USING UTF8) COLLATE utf8_unicode_ci "

MySQL stored procedure reported illegal mix of collations