DROP TABLE IF EXISTS `t1`;
CREATE TABLE `t1` (`col9` set('test1','test2','test3') default NULL,`col20` double default NULL) ENGINE=MyISAM DEFAULT CHARSET=latin1;
INSERT INTO `t1` VALUES ('',NULL);
INSERT INTO `t1` VALUES ('',4294803638.09543);
INSERT INTO `t1` VALUES ('',4294085408.32551);
INSERT INTO `t1` VALUES (NULL,4289863938.50816);
INSERT INTO `t1` VALUES (NULL,4292860452.66918);
INSERT INTO `t1` VALUES ('',1034227.29520554);
INSERT INTO `t1` VALUES (NULL,4290596566.61235);
INSERT INTO `t1` VALUES ('',NULL);
INSERT INTO `t1` VALUES ('',NULL);
INSERT INTO `t1` VALUES ('',3642317.97076327);
INSERT INTO `t1` VALUES (NULL,NULL);
INSERT INTO `t1` VALUES (NULL,4293522773.2092);
INSERT INTO `t1` VALUES ('',NULL);
INSERT INTO `t1` VALUES ('',4293315726.8605);
INSERT INTO `t1` VALUES ('',NULL);
INSERT INTO `t1` VALUES (NULL,4294874078.28254);
INSERT INTO `t1` VALUES ('',NULL);
INSERT INTO `t1` VALUES ('',1489312.21924497);
INSERT INTO `t1` VALUES ('',2678790.02008118);
INSERT INTO `t1` VALUES ('',2715829.4532609);
INSERT INTO `t1` VALUES ('',7837537.40760521);
INSERT INTO `t1` VALUES ('',3834958.88570818);
INSERT INTO `t1` VALUES (NULL,8034477.45472579);
INSERT INTO `t1` VALUES (NULL,4289757998.57863);
INSERT INTO `t1` VALUES (NULL,NULL);
INSERT INTO `t1` VALUES ('',NULL);
INSERT INTO `t1` VALUES (NULL,4287927932.70956);
INSERT INTO `t1` VALUES ('',4290731087.14997);
INSERT INTO `t1` VALUES ('',7192220.37040315);
INSERT INTO `t1` VALUES ('',2145370.0859096);
INSERT INTO `t1` VALUES ('',4289467973.64064);
INSERT INTO `t1` VALUES ('',1228462.63371685);
INSERT INTO `t1` VALUES ('',4287036149.46696);
INSERT INTO `t1` VALUES ('',4292859402.62935);
INSERT INTO `t1` VALUES ('',4291373051.56877);
INSERT INTO `t1` VALUES (NULL,7406926.67394025);
INSERT INTO `t1` VALUES ('',4251681.12616352);
INSERT INTO `t1` VALUES ('',7490398.17004913);
INSERT INTO `t1` VALUES ('',1784120.60319834);
INSERT INTO `t1` VALUES ('',NULL);
INSERT INTO `t1` VALUES (NULL,NULL);
INSERT INTO `t1` VALUES (NULL,1898558.17520676);
INSERT INTO `t1` VALUES ('',4286819333.82577);
INSERT INTO `t1` VALUES ('',760619.523422956);
INSERT INTO `t1` VALUES ('',NULL);
INSERT INTO `t1` VALUES (NULL,4291252767.86138);
INSERT INTO `t1` VALUES (NULL,1154537.93133335);
INSERT INTO `t1` VALUES ('',NULL);

select * from (select str_to_date(col9,col20) as a from t1) a;