【HQL】常用函数

CONCAT_WS(separator, str1, str2,...)

多列转1列，以分割符分割
使用场景：
1.多列在一列显示；
2.多列转多行作为辅助，结合split和explode使用

SELECT DISTINCT a2.dt,a2.userid,type FROM
(
SELECT a1.dt,a1.userid,split(CONCAT_WS(',',a1.a,a1.b,a1.c),',') as types FROM
(select dt,userid,a,b,c from table1
where dt BETWEEN '2018-08-21' and '2018-10-08'
)a1
)a2 lateral VIEW explode (a2.types) a2 AS type