AMXX < 183, MySQL и кириллица

SELECT CONCAT("ALTER TABLE ",TABLE_SCHEMA,".",TABLE_NAME," CHARACTER SET utf8 COLLATE utf8_general_ci;   ",
    "ALTER TABLE ",TABLE_SCHEMA,".",TABLE_NAME," CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci;  ")
    AS alter_sql
FROM information_schema.TABLES
WHERE TABLE_SCHEMA = your_database_name;

CREATE PROCEDURE change_encoding_utf8()
BEGIN
    DECLARE table_name VARCHAR(255);
    DECLARE end_of_tables INT DEFAULT 0;
    DECLARE cur CURSOR FOR
        SELECT t.table_name
        FROM information_schema.tables t
        WHERE t.table_schema = DATABASE() and t.table_type like '%BASE%';
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET end_of_tables = 1;
    
    OPEN cur;
    tables_loop: LOOP
        FETCH cur INTO table_name;
        IF end_of_tables = 1 THEN LEAVE tables_loop; END IF;
        SET @set_alter = CONCAT('alter table ', table_name, ' CHARACTER SET utf8 COLLATE utf8_unicode_ci');
        PREPARE sql_al FROM @set_alter;
        EXECUTE sql_al;
    END LOOP;
    CLOSE cur;
END

call change_encoding_utf8();

-- вместо <Data Base Name> название полное название бд.
alter database <Data Base Name> CHARACTER SET utf8 COLLATE utf8_unicode_ci;