02-28-2008, 08:40 AM
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 Re: Should I specify the CHARACTER SET & COLLATE for UTF8 contents?
Axel Schwenke ¼g¹D¡G
> "howa" <howachen@gmail.com> wrote:
> > Axel Schwenke =BCg=B9D=A1G
> >
> > 1. if we designed some columns might need to store UTF8 character,
> > should we define the whole DB as UTF8, or just define UTF8 in the
> > column definition? Which one is recommeded? for performance, for
> > reliablity?
>
> The encoding/collation is an attribute of the column. Each string-type
> column has this attribute set when it is created. This attribute can
> only be changed with an explicite ALTER TABLE statement. The encoding
> setting of a column - and only this - determines how to store data in
> this column.
>
> The encoding/collation setting for table, database and server is just
> a fallback that is used if you create a column without specifying an
> encoding. You can change the encoding/collation setting of a table,
> a database or the whole server - and no data will actually change.
>
> The recommendation is to use an 8-bit encoding (and any collation)
> for server, database and table. So if you forget to specify the
> encoding for a new column, it will get a space-saving 8-bit encoding.
> However, if your application demands utf8 for *all* columns anyway,
> there is no problem to set the defaults to utf8.
>
> Just keep in mind that utf8 is expensive. Use it - for columns -
> only where neccessary. Setting just the table or database encoding
> to utf8 has no performance implication at all.
>
> > 2. Suppose my DB is defined as latin, but a table is UTF8, how to
> > mysqlimport from a UTF8 text file to the UTF8 table? Currently, I found
> > NO WAY to do so unless I alter the DB character set to UTF8. Since
> > mysqlimport will simply ignore the table definition of UTF8, it will
> > just use the DB default character set, and it is confusing.
>
> If you use LOAD DATA INFILE regularly to load utf8 encoded data,
> this would be a good reason to set the database encoding to utf8.
>
>
> XL
> --
> Axel Schwenke, Senior Software Developer, MySQL AB
>
> Online User Manual: http://dev.mysql.com/doc/refman/5.0/en/
> MySQL User Forums: http://forums.mysql.com/
Thanks so much!  |