Difference between nvarchar2( 10) and varchar2( 10 char)

Question

Hi ,
I had to enhance my application's DB to support unicode data entries(Multilingual data entries) and retrieval. I want to know the basic difference between the following data type decalrations:
nvarchar2( 10) and varchar2( 10 char)
Can any one suggest me which would be a optimum choice?
regards,
Siddarth

Answer 1

Yes, you are almost correct.
Can you read Japanese Character ? (There is no need to understand Japanese words meanings).
Are you ready? Let's go!
SQL> create table tab_size(col varchar(3));
Table created.
SQL> insert into tab_size values ('abc');
1 row created.
SQL> insert into tab_size values ('abcd');
insert into tab_size values ('abcd')
ERROR at line 1:
ORA-12899: value too large for column "USHI"."TAB_SIZE"."COL" (actual: 4, maximum: 3)
SQL> insert into tab_size values('ｱｲｳ'); /* This is  3 characters (3byte) */
1 row created.
SQL> insert into tab_size values('ｱｲｳｴ'); /* This is  4 characters (4byte) */
insert into tab_size values('ｱｲｳｴ')
ERROR at line 1:
ORA-12899: value too large for column "USHI"."TAB_SIZE"."COL" (actual: 4, maximum: 3)
SQL> insert into tab_size values ('あ'); /* This is 1 character (2bytes) */
1 row created.
SQL> insert into tab_size values ('あい'); /* This is 2 characters (4bytes) */
insert into tab_size values ('あい')
ERROR at line 1:
ORA-12899: value too large for column "USHI"."TAB_SIZE"."COL" (actual: 4, maximum: 3)
SQL> insert into tab_size values ('aあ'); /* This is 2 characters (3bytes) */
1 row created.
SQL> insert into tab_size values ('abあ'); /* This is 3 characters (4bytes) */
insert into tab_size values ('abあ')
ERROR at line 1:
ORA-12899: value too large for column "USHI"."TAB_SIZE"."COL" (actual: 4, maximum: 3)
SQL> drop table tab_size;
Table dropped.
SQL> create table tab_char (col varchar2(3 char));
Table created.
SQL> insert into tab_char values ('abc');
1 row created.
SQL> insert into tab_char values ('abcd');
insert into tab_char values ('abcd')
ERROR at line 1:
ORA-12899: value too large for column "USHI"."TAB_CHAR"."COL" (actual: 4,
maximum: 3)
SQL> insert into tab_char values ('あいう');  /* This is 3 characters (6bytes) */
1 row created.
SQL> insert into tab_char values ('あいうえ'); /* This is 4 characters (8bytes) */
insert into tab_char values ('あいうえ')
ERROR at line 1:
ORA-12899: value too large for column "USHI"."TAB_CHAR"."COL" (actual: 4, maximum: 3)
SQL> insert into tab_char values ('aあい'); /* This is 3 characters (5bytes) */
1 row created.
SQL> insert into tab_char values ('abあい'); /* This is 4 characters (6bytes) */
insert into tab_char values ('abあい')
ERROR at line 1:
ORA-12899: value too large for column "USHI"."TAB_CHAR"."COL" (actual: 4, maximum: 3)谢谢。
ありがとう。
Thank you for reading.