SQL> create table test.test1 (itime varchar2(30));

Table created.

SQL> insert into test.test1 values('20220113');

1 row created.

SQL> commit;

Commit complete.

SQL> select itime from test.test1;

ITIME
------------------------------
20220113

SQL> select to_number(itime) from test.test1;

TO_NUMBER(ITIME)
----------------
        20220113
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需要注意的是，被转换的字符串必须符合数值类型格式,如果被转换的字符串不符合数值型格式，Oracle 将抛出错误提示

SQL> insert into test.test1 values('20220113 13:08:00');

1 row created.

SQL> commit;

Commit complete.

SQL> select itime from test.test1;

ITIME
------------------------------
20220113
20220113 13:08:00

SQL> select to_number(itime) from test.test1;
ERROR:
ORA-01722: invalid number


no rows selected
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这样不符合的字符就会报无效的数字。无过多研究，仅供参考！