How to get first and last record in HiveSQL if key is different - sql

Question

I need to get the first and last record for a user if one of the key fields is different over time using a Hive table:
This is some sample data:
UserID EntryDate Activity
a3324 1/1/16 walk
a3324 1/2/16 walk
a3324 1/3/16 walk
a3324 1/4/16 run
a5613 1/1/16 walk
a5613 1/2/16 walk
a5613 1/3/16 walk
a5613 1/4/16 walk
And I'm looking for output preferably like this:
a3324 1/1/16 walk 1/4/16 run
Or at least like this:
a3324 walk run
I start writing code like this:
SELECT UserID, MINIMUM(EntryDate), MAXIMUM(EntryDate), Activity
FROM
SELECT UserID, DISTINCT Activity
GROUP BY UserID
HAVING Count(Activity) > 1
But I know that's not it.
I'd also like to be able to specify the cases where the original activity was Walk and the second activity was Run perhaps in the Where clause.
Can you help with an approach?
Thanks

Answer 1

You can use lag /lead to get a solution
SELECT * FROM (
select UserID ,EntryDate , Activityslec,
lead(Activityslec, 1) over (UserID ,EntryDate ) as nextActivityslec
from table) as A
where Activityslec <> nextActivityslec

Answer 2

SELECT
t.UserId
,MIN(CASE WHEN t.RowNumAsc = 1 THEN t.EntryDate END) as MinEntryDate
,MIN(CASE WHEN t.RowNumAsc = 1 THEN t.Activity END) as MinActivity
,MAX(CASE WHEN t.RowNumDesc = 1 THEN t.EntryDate END) as MaxEntryDate
,MAX(CASE WHEN t.RowNumDesc = 1 THEN t.Activity END) as MaxActivity
FROM
(
SELECT
UserId
,EntryDate
,Activity
,ROW_NUMBER() OVER (PARTITION BY UserId ORDER BY EntryDate) as RowNumAsc
,ROW_NUMBER() OVER (PARTITION BY UserId ORDER BY EntryDate DESC) as RowNumDesc
FROM
Table
) t
WHERE
t.RowNumAsc = 1
OR t.RowNumDesc = 1
GROUP BY
t.UserId
Looks like window functions are supported (https://cwiki.apache.org/confluence/display/Hive/LanguageManual+WindowingAndAnalytics) so using 2 row numbers 1 for EntryDate Ascending and another for Descending with Conditional Aggregation should get you to the answer.
And if you don't want to use Analytic Functions (window functions) you can use self left joins and conditional aggregation:
SELECT
t.UserId
,MIN(CASE WHEN mn.UserId IS NULL THEN t.EntryDate END) as MinEntryDate
,MIN(CASE WHEN mn.UserId IS NULL THEN t.Activity END) as MinActivity
,MAX(CASE WHEN mx.UserId IS NULL THEN t.EntryDate END) as MaxEntryDate
,MAX(CASE WHEN mx.UserId IS NULL THEN t.Activity END) as MaxActivity
FROM
Table t
LEFT JOIN Table mn
ON t.UserId = mn.UserId
AND t.EntryDate > mn.EntryDate
LEFT JOIN Table mx
ON t.UserId = mx.UserId
AND t.EntryDate < mx.EntryDate
WHERE
mn.UserId IS NULL
OR mx.UserId IS NULL
GROUP BY
t.UserId
Or a correlated Sub Query way:
SELECT
UserId
,MIN(EntryDate) as MinEntryDate
,(SELECT
Activity
FROM
Activity a
WHERE
u.UserId = a.UserId
AND a.EntryDate = MIN(u.EntryDate)
LIMIT 1
) as MinActivity
,MAX(EntryDate) as MaxEntryDate
,(SELECT
Activity
FROM
Activity a
WHERE
u.UserId = a.UserId
AND a.EntryDate = MAX(u.EntryDate)
LIMIT 1
) as MaxActivity
FROM
Activity u
GROUP BY
UserId