Raffaele,

    thanks for your answer.
    The question is what prevents data loss in the first procedure ?
    Suppose the filed in question is

    FIRST_NAME VARCHAR(60) CHARACTER SET NONE

    so lets create a temporary field

    TMP_NAME VARCHAR(60) CHARACATER SET ISO8859_1

    and then lets fill it

    UPDATE TABLE1 SET TMP_NAME = CAST(FIRST_NAME AS VARCHAR(60) CHARACTER SET OCTETS)

Whichever character (from 0 to 255) were in FIRST_NAME would be blindly copied to TMP_NAME.
This has the same effect as assuming that the characters in FIRST_NAME where loaded as ISO8859_1, so simply changing FIRST_NAME type from NONE to ISO8859_1 would be equivalent.

Aldo

 

The first procedure provides you safe from data loss.
you can directly execute the change of the charset after doing a complete
backup of the database.




-------Messaggio originale-------

Da: Aldo Caruso aldo.caruso@... [firebird-support]
Data: 21/07/2015 18.38.39
A: firebird-support@yahoogroups.com
Oggetto: [firebird-support] Chararacter set NONE to ISO8859_1

Hi,

I have some VARCHAR fields whose character set were incorrectly
defined as NONE. I would like to use ISO8859_1 instead.

I read on "The Firebird Book" that in order to do so you must add a
new temporary field, with the right character set, fill it with the data
from the original field ( using OCTECT as an intermediat chararacter set
) and finally drop and recreate the original field with the right
character set, filling it with the data that was stored in the temporary
field. The process ends up dropping the temporary field.

I wonder what is wrong with simply invoking "ALTER TABLE X ALTER
COLUMN Y TYPE CHAR(N) CHARACTER SET ISO8859_1"

Thanks in advance for any help.

Aldo Caruso



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