[Info-ingres] Micro-madness

[Paul A.]

Choose one representation and change the codes, use an insert/modify 
rule to force consistency?

On 17/06/2021 14:17, Martin Bowes wrote:
>
> I’m seeing some progress…nvarchar stores Unicode points as UTF-8.
>
> And:
>
> The UTF-8 encoding of mu (U+03BC) is 0xCE 0xBC
>
> https://www.utf8-chartable.de/unicode-utf8-table.pl?start=896&number=128&names=-&utf8=0x
>
> Also the UTF-8 encoding of mu(U+00B5) is 0xC2 0xB5
>
> https://www.utf8-chartable.de/unicode-utf8-table.pl?start=128&number=128&names=-&utf8=0x
>
> So we have two Unicode code points for mu…why I know not.
>
> And I still don’t know how to get them to equate.
>
> Marty
>
> *From:*Tony Douglas <tonyd08068 at netscape.net>
> *Sent:* 17 June 2021 14:05
> *To:* Martin Bowes <martin.bowes at ndph.ox.ac.uk>
> *Cc:* info-ingres at lists.planetingres.org
> *Subject:* Re: [Info-ingres] Micro-madness
>
> Unicode…. There be dragons. Might be something to do with 
> normalisation form - NFC and NFD say how codes can combine to form 
> different characters - this page 
> https://www.win.tue.nl/~aeb/linux/uc/nfc_vs_nfd.html 
> <https://www.win.tue.nl/~aeb/linux/uc/nfc_vs_nfd.html> might help, or 
> it might not - I was just about getting unconfused with the 
> terminology of Unicode when I stopped looking at it a few years ago :( 
> But weird things could happen. Have you tried a UTF8 client to see 
> what happens (assuming you’ve got an installation where 
> transliteration is available) ?
>
> Looking forward to seeing how this pans out !
>
> Thanks,
>
> - Tony
>
> Sent from my iPhone
>
>
>
>     On 17 Jun 2021, at 13:54, Martin Bowes <martin.bowes at ndph.ox.ac.uk
>     <mailto:martin.bowes at ndph.ox.ac.uk>> wrote:
>
>     
>
>     Hi All,
>
>     Can someone please explain this one…please use small words…
>
>     My Linux installation is an ISO-8859-1 charset. We have a  table
>     which has an nvarchar(20) column.
>
>     Now the Greek mu symbol is U+00B5, a capital-A with a circumflex
>     is 00C2, The ¼ is U+00BC, and a capital-I with a circumflex is U+00CE.
>
>     And in _terminal monitor_ connection, how does this work…
>
>     select U&'\00c2', U&'\00b5', U&'\00c2\00b5'\g
>
>     ┌──────┬──────┬──────┐
>
>     │col1  │col2  │col3  │
>
>     ├──────┼──────┼──────┤
>
>     │▒     │▒     │µ    │
>
>     └──────┴──────┴──────┘
>
>     (1 row)
>
>     select u&'\00ce', u&'\00bc', u&'\00ce\00bc'\g
>
>     ┌──────┬──────┬──────┐
>
>     │col1  │col2  │col3  │
>
>     ├──────┼──────┼──────┤
>
>     │▒     │▒     │μ    │
>
>     └──────┴──────┴──────┘
>
>     (1 row)
>
>     So two weird codes have both combined to make a mu. I didn’t just
>     invent these. I got them from two distinct data sets which were
>     being compared.
>
>     And they are clearly not the same thing.
>
>     create table test(id integer1, a nvarchar(20));
>
>     insert into test values (1, U&'\00c2\00b5'), (2, U&'\00ce\00bc');
>
>     select * from test\g
>
>     ┌──────┬────────────────────────────────────────┐
>
>     │id │a                                       │
>
>     ├──────┼────────────────────────────────────────┤
>
>     │ 1│µ                                      │
>
>     │     2│μ           │
>
>     └──────┴────────────────────────────────────────┘
>
>     (2 rows)
>
>     select a, count(1) from test group by a\g
>
>     ┌────────────────────────────────────────┬─────────────┐
>
>     │a │col2         │
>
>     ├────────────────────────────────────────┼─────────────┤
>
>     │µ │            1│
>
>     │μ │            1│
>
>     └────────────────────────────────────────┴─────────────┘
>
>     (2 rows)
>
>     So could someone please explain this, and also how I can write
>     some code which will say these two mu’s are the same thing.
>
>     Marty
>
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