DB="database_name"
USER="mysql_user"
PASS="mysql_password"
(
    echo 'ALTER DATABASE `'"$DB"'` CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;'
    mysql -p$PASS -u $USER "$DB" -e "SHOW TABLES" --batch --skip-column-names \
    | xargs -I{} echo 'ALTER TABLE `'{}'` CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;'
) \
| mysql -p$PASS -u $USER "$DB"


To get the script you work open your command line and use the following steps:
1. nano utf.sh
2. paste the script & save
3. sudo chmod 755 utf.sh (in terminal)
5. run the script by type ./utf.sh

Yes, collation has been changed!