Fill field with first value

[cxs6345]

I have a data set for web traffic.  A sessionID ties all traffic for an individual browsing session together - all events from the time you open a new tab until you close it.  There is also a memberID field.  Some records do NOT have a value populated for memberID, so I want to return each record for the sessionID with the FIRST non-null value found in the sessionID.  For instance

time	sessionID	memberID	evalField
12:01	1	<NULL>	abc
12:02	1	<NULL>	abc
12:03	1	abc	abc
12:04	1	<NULL>	abc

Can someone help me out with how to get this evalField column?  Thanks so much!

[PickleRick · Accepted solution]

That's job for eventstats.

<your search>
| eventstats first(memberID) as memberID by sessionID