kylin计算两列时间相差天数

select TIMESTAMPDIFF(day,date'2012-01-01', date '2014-02-01')

执行结果：

*****_EXTERNAL两列时间 ADMISSION_TIME和DISCHARGE_TIME 为varchar类型：

查询*****_EXTERNAL表数据：

select * from ***_EXTERNAL where VISIT_ID='2626780';

执行sql

select TIMESTAMPDIFF(day, CAST(ADMISSION_TIME AS timestamp),CAST(DISCHARGE_TIME AS timestamp))  from ***_EXTERNAL where VISIT_ID='2626780';

执行结果：