The difference between countDistinct and distinct.count

Question

Why do I get different outputs for ..agg(countDistinct(\"member_id\") as \"count\") and ..distinct.count? Is the difference the same as between

Answer 1

1st command :

DF.agg(countDistinct("member_id") as "count")

return the same as that of select count distinct(member_id) from DF.

2nd command :

DF.distinct.count

is actually getting distinct records or removing al duplicates from the DF and then taking the count.