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Editorial Team
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Asked: 2026-05-31T23:17:09+00:00

I have a code: CREATE TABLE IF NOT EXISTS Person ( name varchar(24) …

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I have a code:

CREATE TABLE IF NOT EXISTS Person
(
   name varchar(24) ...
)
CHARACTER SET utf8 COLLATE utf8_polish_ci;

This works OK in my application, but I read if someone put in name field a string that contains character wchich code is greater than 127, database will use 2 bytes (or more) to store this character. So i think, i will change character set to utf16:

CHARACTER SET utf16 COLLATE utf16_polish_ci;

But now when I run my application, exception apears: KeyNotFoundException. It apears exactly at these instructions:

MySqlCommand komenda = baza.Połączenie.CreateCommand ();
komenda.CommandText  = zapytanie;

MySqlDataReader dr = komenda.ExecuteReader (); // HERE, at execute reader method

if (dr.Read ()) ...

1) Anyone had similar problem? 2) Any idea how to use always 2 bytes/char in database field?

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1 Answer

  1. Editorial Team

    I’m not sure I understand why you’re converting from UTF-8 to UTF-16. I’m assuming you’re worried that any characters that require two bytes or more to store, won’t fit in a UTF-8 encoding. This is not the case. In MySQL UTF-8 values can be stored with one, two, or three bytes. Unicode points U+0000 to U+007F take 1 byte and points U+0080 to U+07FF take 2 bytes–this range covers the Polish alphabet. Since the majority of characters in the Polish alphabet take 1 byte to store you should probably stick with UTF-8 and save some memory. However, if you want to always use 2 bytes, at the cost of wasted space, you could stick with UTF-16.

    Here are some helpful links:

    Unicode support in MySQL: http://dev.mysql.com/doc/refman/5.6/en/charset-unicode.html

    Basic Unicode Overview : http://www.joelonsoftware.com/articles/Unicode.html

    As for the exception, and this is purely a guess, it may have something to do with trying to read data that is UTF-8 encoded as if it were UTF-16 encoded. Did you change the character set after you already had UTF-8 encoded data in your table?

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