Why Do UTF-8 Characters Appear as \'?\' When Fetched from MySQL in R?

Why Do UTF-8 Characters in MySQL Appear as "?" When Fetched in R?

Fetching UTF-8 encoded text from MySQL in R often leads to the display of "?" for non-ASCII characters. This issue arises due to a mismatch between the default locale in R and the session character set used by MySQL.

Encoding Compatibility Issues

When running R on OS X with the default en_US.UTF-8 locale, the R session expects UTF-8 encoded data by default. However, the MySQL connection established using ODBC or RMySQL may use a different character set, such as latin1. This mismatch causes incorrect decoding of UTF-8 characters.

Solutions

To rectify this issue, ensure that the MySQL connection uses the UTF-8 character set:

• RMySQL: After establishing the connection, execute the query SET NAMES utf8 to change the session character set to UTF-8.
• RODBC: Connect using CharSet=utf8 in the DSN string to specify the UTF-8 character set during connection.

Additional Tips

• Check the character set of the MySQL database and table. They should also be set to UTF-8.
• Use the Encoding function in R to convert the character encoding if necessary.
• Set the options(encoding) configuration in R to UTF-8 to ensure consistent UTF-8 encoding throughout the session.

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