const char *
mysql_stmt_error(MYSQL_STMT *stmt)
          For the statement specified by stmt,
          mysql_stmt_error() returns a
          null-terminated string containing the error message for the
          most recently invoked statement API function that can succeed
          or fail. An empty string ("") is returned
          if no error occurred. Either of these two tests can be used to
          check for an error:
        
if(*mysql_stmt_errno(stmt))
{
  // an error occurred
}
if (mysql_stmt_error(stmt)[0])
{
  // an error occurred
}
          If the failed statement API function was
          mysql_stmt_close(), do not
          call mysql_stmt_error() to
          obtain error information because
          mysql_stmt_close() makes the
          statement handler invalid. Call
          mysql_error() instead.
        
The language of the client error messages may be changed by recompiling the MySQL client library. You can choose error messages in several different languages.