MySQL 5.0 Reference Manual  /  ...  /  Unicode Support

10.1.10 Unicode Support

MySQL supports two character sets for storing Unicode data:

  • ucs2, the UCS-2 encoding of the Unicode character set using 16 bits per character

  • utf8, a UTF-8 encoding of the Unicode character set using one to three bytes per character

These two character sets support the characters from the Basic Multilingual Plane (BMP) of Unicode Version 3.0. BMP characters have these characteristics:

  • Their code values are between 0 and 65535 (or U+0000 .. U+FFFF)

  • They can be encoded with a fixed 16-bit word, as in ucs2

  • They can be encoded with 8, 16, or 24 bits, as in utf8

  • They are sufficient for almost all characters in major languages

The ucs2 and utf8 character sets do not support supplementary characters that lie outside the BMP. Characters outside the BMP compare as REPLACEMENT CHARACTER and convert to '?' when converted to a Unicode character set.

A similar set of collations is available for each Unicode character set. For example, each has a Danish collation, the names of which are ucs2_danish_ci and utf8_danish_ci. All Unicode collations are listed at Section, “Unicode Character Sets”.

The MySQL implementation of UCS-2 stores characters in big-endian byte order and does not use a byte order mark (BOM) at the beginning of values. Other database systems might use little-endian byte order or a BOM. In such cases, conversion of values will need to be performed when transferring data between those systems and MySQL.

MySQL uses no BOM for UTF-8 values.

Client applications that need to communicate with the server using Unicode should set the client character set accordingly; for example, by issuing a SET NAMES 'utf8' statement. ucs2 cannot be used as a client character set, which means that it does not work for SET NAMES or SET CHARACTER SET. (See Section 10.1.4, “Connection Character Sets and Collations”.)

The following sections provide additional detail on the Unicode character sets in MySQL.

User Comments
  Posted by Haakon Meland Eriksen on January 24, 2006
Connect with the same characterset as your data to display correctly. This example connects to the MySQL-server using UTF-8:

mysql --default-character-set=utf8 -uyour_username -p -h your_database

If you get into trouble from a PHP-based web application, check the characterset configurations of these components:

1) the MySQL database
2) php.ini
3) httpd.conf
4) your server

  Posted by lorenz pressler on May 2, 2006
if you get data via php from your mysql-db (everything utf-8)
but still get '?' for some special characters in your browser
(<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />),
try this:

after mysql_connect() , and mysql_select_db() add this lines:
mysql_query("SET NAMES utf8");

worked for me.
i tried first with the utf8_encode, but this only worked for äüöéè...
and so on, but not for kyrillic and other chars.
  Posted by Eliram on August 6, 2008
I had a problem submitting unicode data from ASP pages to the MySQL server while everything was set to utf8 .

It turns out the problem was that my ODBC driver was version 3.5.1 and that's what caused the problem. Installing version 5.1 solved the problem.
  Posted by David Busby on August 3, 2012
As of mySQL 5.x you can use the init_connect commands to force UTF-8 compliance from any client connection.

I have blogged about this here:

Removing the need to use SET NAME in your PHP/ASP/Ruby/C++ code.

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