Re: Primary Key validation error on Unicode strings

From: Jon Hanna (
Date: Thu Nov 12 2009 - 04:13:32 CST

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    Wunna Ko wrote:
    > While I am working on Unicode strings with MS Database 2005, I got
    > primary key validation error when I input Burmese characters ကု "Ku"
    > while ကို "Ko" is in the database.
    > ကု "Ku" is U1000 + U102F and ကို "Ko" is U1000 + U102D + U102F
    > It is really a separate string but MS Database treat as a same string. :(

    It's more accurate to say that the database is treating it as an
    equivalent string. Which are considered equivalent depends on the
    collation. The code:

    NCHAR(0x1000) + NCHAR(0x102F) COLLATE Latin1_General_BIN =
            NCHAR(0x1000) + NCHAR(0x102D) + NCHAR(0x102F)
    THEN 'Equivalent' ELSE 'Distinct'
    NCHAR(0x1000) + NCHAR(0x102F) COLLATE Latin1_General_CI_AS =
    NCHAR(0x1000) + NCHAR(0x102D) + NCHAR(0x102F)
    THEN 'Equivalent' ELSE 'Distinct'

    gives results of "Distinct, Equivalent" because the first collation
    considers these strings distinct while the second doesn't.

    Without a COLLATE clause the default collation for your database will be

    Similarly, if a column is a primary key, then the collation used for
    that column will affect which strings are considered equivalent for the
    purpose of that key.

    SELECT * FROM fn_helpcollations() will list collations available on your
    Those found with SELECT * FROM fn_helpcollations() WHERE description
    LIKE '%bin%' are most likely to find these two strings to be distinct,
    but may go too far in this regard (being sensitive to all concerns of
    case, accent, etc).

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