结论: UTF-8字符集: 一个汉字占三个字节 GBK字符集：一个汉字占二个字节

验证： oracle AMERICAN_AMERICA.AL32UTF8字符集下 一个汉字占3个字节

SQL> select userenv('language') from dual;  

USERENV('LANGUAGE')
----------------------------------------------------
AMERICAN_AMERICA.AL32UTF8


SQL> select lengthb('你') from dual;  

LENGTHB('你')
------------
           3

SQL> select lengthb('你好') from dual;

LENGTHB('你好')
---------------
              6

创建测试表,针对grade字段varchar(4)变量验证：

create table test1.test001 (id number(10) primary key ,name varchar(8),grade VARCHAR(4));

SQL> insert into test1.test001 values(1,'maomao','您好');
insert into test1.test001 values(1,'maomao','您好')
                                            *
ERROR at line 1:
ORA-12899: value too large for column "TEST1"."TEST001"."GRADE" (actual: 6,
maximum: 4)

报错提示varchar(4)最大时4字节,然而插入'您好'2个汉字占用6字节， 修改字段grade varchar变量值为6个字节

SQL> alter table test1.test001  modify GRADE VARCHAR(6);
Table altered.

SQL> insert into test1.test001 values(1,'maomao','您好');

1 row created.

SQL> commit;

Commit complete.

SQL> select * from test1.test001;

        ID NAME     GRADE
---------- -------- ------
         1 maomao   您好

oracle AMERICAN_AMERICA.ZHS16GBK字符集下 一个汉字占2个字节:

SQL> select userenv('language') from dual;  

USERENV('LANGUAGE')
--------------------------------------------------------------------------------
AMERICAN_AMERICA.ZHS16GBK

SQL> select lengthb('你') from dual;  

LENGTHB('你')
-------------
            2
			

SQL> select lengthb('你好') from dual;

LENGTHB('你好')
---------------
              4

创建测试表test02， 字段grade变量VARCHAR(4) 为4字节,插入'你好'2个汉字,由于库是 AMERICAN_AMERICA.ZHS16GBK字符集,'你好'正好是4字节,插入成功

SQL> create table test1.test002 (id number(10) primary key ,name varchar(8),grade VARCHAR(4));

Table created.

SQL> insert into test1.test002 values(1,'maomao','您好');

1 row created.

SQL> select * from test1.test002;

        ID NAME                     GRADE
---------- ------------------------ ------------
         1 maomao                   您好

验证得到的结论是正确的,验证结束。