-- 测试脚本如下：
-- 字符集WE8ISO8859P1，国家字符集AL16UTF16
-- nchar类型
set NLS_LANG=AMERICAN_AMERICA.WE8ISO8859P1
drop table utf16_1;
create table utf16_1 (nc1 nchar(1),nc2 nchar(2),nc3 nchar(3) );
insert into utf16_1 values('a','测','从1');

dump结果：
select dump(nc1),dump(nc2),dump(nc3) from utf16_1;

Typ=96 Len=2: 0,97
Typ=96 Len=4: 0,178,0,226
Typ=96 Len=6: 0,180,0,211,0,49

-- char类型
drop table utf16_2;
create table utf16_2 (c1 char(1),c2 char(2),c3 char(3) );
insert into utf16_2 values('a','测','从1');

dump结果：
select dump(c1),dump(c2),dump(c3) from utf16_2;

Typ=96 Len=1: 97
Typ=96 Len=2: 178,226
Typ=96 Len=3: 180,211,49

结论：ISO8859P1这类单字节字符集，nchar和char的区别是nchar双字节保存，char单字节保存，字符编码一样。

-- 字符集ZHS16GBK，国家字符集AL16UTF16
set NLS_LANG=AMERICAN_AMERICA.ZHS16GBK
-- nchar类型
drop table utf16_1;
create table utf16_1 (nc1 nchar(1),nc2 nchar(2),nc3 nchar(3) );
insert into utf16_1 values('a','测','从1');

dump结果：
select dump(nc1),dump(nc2),dump(nc3) from utf16_1;

Typ=96 Len=2: 0,97
Typ=96 Len=4: 109,75,0,32
Typ=96 Len=6: 78,206,0,49,0,32

-- char类型
drop table utf16_2;
create table utf16_2 (c1 char(1),c2 char(2),c3 char(3) );
insert into utf16_2 values('a','测','从1');

dump结果：
select dump(c1),dump(c2),dump(c3) from utf16_2;

Typ=96 Len=1: 97
Typ=96 Len=2: 178,226
Typ=96 Len=3: 180,211,49