How to create select SQL statement that would produce "merged" dataset from two tables(Oracle DBMS)?
- by Roman Kagan
Here's my original question:
merging two data sets
Unfortunately I omitted some intircacies, that I'd like to elaborate here.
So I have two tables events_source_1 and events_source_2 tables. I have to produce the data set from those tables into resultant dataset (that I'd be able to insert into third table, but that's irrelevant).
events_source_1 contain historic event data and I have to do get the most recent event (for such I'm doing the following:
select event_type,b,c,max(event_date),null next_event_date
from events_source_1
group by event_type,b,c,event_date,null
events_source_2 contain the future event data and I have to do the following:
select event_type,b,c,null event_date, next_event_date
from events_source_2
where b>sysdate;
How to put outer join statement to fill the void (i.e. when same event_type,b,c found from event_source_2 then next_event_date will be filled with the first date found
GREATLY APPRECIATE FOR YOUR HELP IN ADVANCE.
