Quick script:

SET FOREIGN_KEY_CHECKS = 0; 
SET @tables = NULL;
SELECT GROUP_CONCAT('`', table_schema, '`.`', table_name, '`')     INTO @tables
  FROM information_schema.tables 
  WHERE table_schema = 'database_name'; -- specify DB name here.

SET @tables = CONCAT('DROP TABLE ', @tables);
PREPARE stmt FROM @tables;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
SET FOREIGN_KEY_CHECKS = 1; 

SET SERVEROUTPUT ON SIZE 1000000
BEGIN
  FOR cur_rec IN (SELECT object_name, object_type 
                  FROM   user_objects
                  WHERE  object_type IN ('TABLE', 'VIEW', 'PACKAGE', 'PROCEDURE', 'FUNCTION', 'SEQUENCE')) LOOP
    BEGIN
      IF cur_rec.object_type = 'TABLE' THEN
        EXECUTE IMMEDIATE 'DROP ' || cur_rec.object_type || ' "' || cur_rec.object_name || '" CASCADE CONSTRAINTS';
      ELSE
        EXECUTE IMMEDIATE 'DROP ' || cur_rec.object_type || ' "' || cur_rec.object_name || '"';
      END IF;
    EXCEPTION
      WHEN OTHERS THEN
        DBMS_OUTPUT.put_line('FAILED: DROP ' || cur_rec.object_type || ' "' || cur_rec.object_name || '"');
    END;
  END LOOP;
END;
/

Pour droper tous les schémas d'un coup (avant un restore par exemple)
(Ajout de autour du nom de la table") mysql -uroot -p<password> -e "show databases" | grep -v Database | grep -v mysql| grep -v information_schema | grep -v performance_schema | grep -v test|gawk '{print "drop database" $1 "`;select sleep(0.1);"}' | mysql -uroot -p<password>