Question

I looked in the mysql reference, and here, in stackoverflow, and looks like a lot of people are having difficulties with character encoding, but I couldn’t find a clear answer to this problem:

A java program is using a mysql database, and when there are special characters in the query like ű,ő (but á,é,í,ó,ú works), it throws an SQLException:

    Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
    Connection conn = DriverManager.getConnection(
            "jdbc:odbc:<database>", "<user>", "<pass>"
            );

    PreparedStatement stmt = conn.prepareStatement(
            " select username, priority " +
            " from users " +
            " where username like ?");
            //" where username like ? collate latin2_general_ci");
    stmt.setString(1, "Ernő");
    ResultSet rs = stmt.executeQuery();
    while(rs.next()) {
        System.out.println(rs.getString("username") + "  " + rs.getInt("priority"));
    }

Exception:

Exception in thread "main" java.sql.SQLException:
[MySQL][ODBC 5.1 Driver][mysqld-5.1.63-0ubuntu0.10.04.1]
Illegal mix of collations (latin2_hungarian_ci,IMPLICIT)
and (latin1_swedish_ci,COERCIBLE) for operation 'like'

The table structure is:

CREATE TABLE `users` (
`username` varchar(45) COLLATE latin2_hungarian_ci NOT NULL,
`password` varchar(45) COLLATE latin2_hungarian_ci NOT NULL,
`priority` tinyint(4) NOT NULL,
`idCimlistaFK` int(10) unsigned DEFAULT NULL,
`timestamp` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
PRIMARY KEY (`username`),
KEY `fk_users_tbl_Cimlista1` (`idCimlistaFK`),
CONSTRAINT `fk_users_tbl_Cimlista1` FOREIGN KEY (`idCimlistaFK`)
REFERENCES `tbl_cimlista` (`id_Cimlista`) ON DELETE NO ACTION ON UPDATE NO ACTION
) ENGINE=InnoDB DEFAULT CHARSET=latin2 COLLATE=latin2_hungarian_ci 

When I tried to force a collation like in the commented line:

" where username like ? collate latin2_general_ci");

It also throws an exception:

COLLATION 'latin2_general_ci' is not valid for CHARACTER SET 'latin1'

Does anyone know, how to solve this (possibly within java)? (I would prefer not to change the database, because it’s a legacy system.)

UPDATE:

I used the following url, as suggested by Rahul Agrawal:

"jdbc:mysql://localhost:3306/database?characterEncoding=latin2"

It did work, however, I noticed a sideeffect.
When I updated and inserted data with the testserver, wich runs mysql on a win XP machine, it went fine. But when I updated and inserted the data to the production server running Ubuntu, I did get rows, wich had ?-signs instead ő,ű-letters. I resolved this with a workaround since, but it would be nice to see and understand, what went wrong, what are the issues here.

Answer 1

You need to use UTF-8 charset

In Connection URL try this

jdbc:mysql://localhost:3306/testdb?characterEncoding=utf8

Database CHARSET=utf8

Database Collation = utf8_general_ci