在这种情况下，不需要删除列;你可以直接修改它

SQL> create table test (col number(3));

Table created.

SQL> insert into test values (123);

1 row created.

SQL> create or replace view v_test as select * From test;

View created.

SQL> select * from v_test;

       COL
----------
       123

SQL> desc v_test
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 COL                                                NUMBER(3)

SQL> alter table test modify col number(8);

Table altered.

SQL> select * from v_test;

       COL
----------
       123

SQL> desc v_test
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 COL                                                NUMBER(8)

SQL>

即使你通过删除一个列（这可能是一个坏主意，因为你丢失了存储在其中的数据），视图也应该自动反映数据类型的变化：

SQL> create table test (id number, col number(3));

Table created.

SQL> insert into test values (1, 123);

1 row created.

SQL> create or replace view v_test as select * from test;

View created.

SQL> select * From v_test;

        ID        COL
---------- ----------
         1        123

SQL> desc v_test
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 ID                                                 NUMBER
 COL                                                NUMBER(3)    --> number (3)

删除该列并将其放回，修改数据类型：

SQL> alter table test drop column col;

Table altered.

SQL> alter table test add col number(8);

Table altered.

检查其数据类型：就像我说的，它会自动反映出来：

SQL> desc v_test
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 ID                                                 NUMBER
 COL                                                NUMBER(8)   --> number (8)

SQL> select * from v_test;

        ID        COL
---------- ----------
         1                       --> COL is empty, though

SQL>