collect_set去除重複元素；collect_list不去除重複元素
select gender,
concat_ws(',', collect_set(children)),
concat_ws(',', collect_list(children))
from Affairs
group by gender
// 建立檢視
data.createOrReplaceTempView("Affairs")
val df3= spark.sql("select gender,concat_ws(',',collect_set(children)),concat_ws(',',collect_list(children)) from Affairs group by gender")
df3: org.apache.spark.sql.DataFrame = [gender: string, concat_ws(,, collect_set(children)): string ... 1 more field]
df3.show // collect_set去除重複元素；collect_list不去除重複元素
+------+-----------------------------------+------------------------------------+
|gender|concat_ws(,, collect_set(children))|concat_ws(,, collect_list(children))|
+------+-----------------------------------+------------------------------------+
|female| no,yes| no,yes,no,no,yes|
| male| no,yes| no,yes,no,yes,no|
+------+-----------------------------------+------------------------------------+