Example script to convert a whole database to a certain charset and collation
cat fixcollaction.bash
#!/bin/bash
DB="$1"
CHARSET="$2"
COLL="$3"
[ -n "$DB" ] || exit 1
[ -n "$CHARSET" ] || CHARSET="utf8mb4"
[ -n "$COLL" ] || COLL="utf8mb4_unicode_ci"
echo $DB
echo "ALTER DATABASE \`$DB\` CHARACTER SET $CHARSET COLLATE $COLL;" | mysql
echo "USE \`$DB\`; SHOW TABLES;" | mysql -s | (
while read TABLE; do
echo $DB.$TABLE
echo "ALTER TABLE \`$TABLE\` CONVERT TO CHARACTER SET $CHARSET COLLATE $COLL;" | mysql $DB
done
)