sql server - SQL Getting unique list and replace nulls

Question

I am working on some data that is structured like this

userid	useremail	username	sessionId	eventTime
		joe	1	2021-01-27 21:03:03.2500000
123	[email protected]		1	2021-01-27 21:05:03.2500000
123	[email protected]	joe	1	2021-01-27 21:03:03.2500000
	[email protected]		2	2021-01-26 21:05:03.2500000
123	[email protected]	joe	2	2021-01-26 21:03:03.2500000
123		joe	2	2021-01-26 21:05:03.2500000
	[email protected]	joe	2	2021-01-26 21:03:03.2500000
123			2	2021-01-26 21:05:03.2500000

question from:https://stackoverflow.com/questions/65927628/sql-getting-unique-list-and-replace-nulls

Answer 1

You can use window functions:

select coalesce(userid, max(userid) over (partition by sessionid)) as userid,
       coalesce(useremail, max(useremail) over (partition by sessionid)) as useremail,
       coalesce(username, max(username) over (partition by sessionid)) as username,
       . . .
from t;