hive sql sum求和返回NULL

使用hive sql求文本文件中金額的總和

文本文件weex.txt
"42" "2017-01-01" "優(yōu)惠券使用金額" "53084.00"
"47" "2017-01-01" "司機(jī)獎(jiǎng)勵(lì)補(bǔ)貼成本" "550.00"

將weex.txt load到hdfs中

sql語(yǔ)句

select sum(amount) from weex;
和select sum(double(amount)) from weex;都嘗試了仍然返回NULL

hive的建表語(yǔ)句

create table weex(id int, s_day string, cost_type string, amount double, createtime string, updatetime string) ROW FORMAT DELIMITED FIELDS TERMINATED BY '\t';