I want to change the character set of Oracle Database (8i). I was trying to change it to TH8TISASCII from WE8ISO8859P1,...
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but it gives an error: "it must be superset of older one," so how can I change it? If WE8ISO8859P1 is a superset then why it is not supporting the Thai language?
Try reading the Oracle8i National Language Support Guide document... it should guide you properly.
Here's an excerpt that is pertinent:
In most cases, you will need to do a full export/import to properly convert all data to the new character set. However, if, and only if, the new character set is a strict superset of the current character set, it is possible to use the ALTER DATABASE CHARACTER SET statement to expedite the change in the database character set.
The target character set is a strict superset if and only if each and every codepoint in the source character set is available in the target character set, with the same corresponding codepoint value. For instance, the following migration scenarios can take advantage of the ALTER DATABASE CHARACTER SET statement because US7ASCII is a strict subset of WE8ISO8859P1, ZHS16GBK, and UTF8:
Table 3-8 Sample Migration Scenarios Current Character Set New Character Set New Character Set is Strict Superset? US7ASCII WE8ISO8859P1 Yes US7ASCII ZHS16GBK Yes US7ASCII UTF8 Yes
ALTER DATABASE [<db_name>] CHARACTER SET <new_character_set>; ALTER DATABASE [<db_name>] NATIONAL CHARACTER SET <new_NCHAR_character_set>;
ALTER DATABASE CHARACTER SET WE8ISO8859P1;
SQL> SHUTDOWN IMMEDIATE; -- or NORMAL <do a full backup> SQL> STARTUP MOUNT; SQL> ALTER SYSTEM ENABLE RESTRICTED SESSION; SQL> ALTER SYSTEM SET JOB_QUEUE_PROCESSES=0; SQL> ALTER DATABASE OPEN; SQL> ALTER DATABASE CHARACTER SET <new_character_set_name>; SQL> SHUTDOWN IMMEDIATE; -- or NORMAL SQL> STARTUP;
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