列类型指定int 与number有什么区别

列类型指定int 与number有什么区别
int和number都是数值类型，int是正整数，number可以允许小数位，number重点在这里不多讲，只是说在不指定参数的情况下有什么区别？
还是老风格，用实例说话
SQL> conn zhang/zhang;
Connected.
SQL> create table tt(id int,id1 number);
Table created.
SQL> desc tt;
Name                                      Null?    Type
----------------------------------------- -------- ----------------------------
ID                                                 NUMBER(38)
ID1                                                NUMBER
SQL> alter table tt add id1 number(38);
alter table tt add id1 number(38)
*
ERROR at line 1:
ORA-01430: column being added already exists in table

SQL> alter table tt add id2 number(38);
Table altered.
SQL> desc tt;
Name                                      Null?    Type
----------------------------------------- -------- ----------------------------
ID                                                 NUMBER(38)
ID1                                                NUMBER
ID2                                                NUMBER(38)
SQL> insert into tt values(1.1,1.1,1.1);
1 row created.
SQL> select * from tt;
ID        ID1        ID2
---------- ---------- ----------
1        1.1          1
SQL>