Joining two tables - Oracle

Question

I have two datasets: A and B

Dataset A:

indiv_id      January     
1000068000004   1   
1000068000011   1   
1000068000012   1

Dataset B:

indiv_id       March     
1000068000003   1   
1000068000011   1   
1000068000015   1

Desired Result:

Indiv_id      January    March    
1000068000003  null       1    
1000068000004   1        null  
1000068000011   1         1   
1000068000012   1        null    
1000068000015  null       1

How do I join the tables so that I have all of the Indiv_IDs from BOTH lists and their values in the column that is distinct to their particular dataset?

Thanks

Answer 1

You can use full join :

select indiv_id, a.january, b.march
from a full join
     b
     using (indiv_id);

The using clause makes this particularly convenient because you don't need to worry about any coalesce() s in the select .

Answer 2

You've got 3 cases to deal with: the ID is in both datasets, the ID is only in dataset A, or the ID is only in dataset B. You can't solve that with select ... from dataset_A left join dataset_B ... because you'll get the first two cases but not the third.

What you need is to define a view that gives you all the IDs across both datasets, then left join to each dataset:

with all_IDs as (select indiv_ID from dataset_A union select indiv_ID from dataset_B)
select indiv_ID, january, march
from all_IDs
left join dataset_A using (indiv_ID)
left join dataset_B using (indiv_ID)