Question

I am trying to write a join statement to join the following three data sets together. (This is using MS SQL Server)

Set 1
ID    Date    Col1 
1     Jan 11  a1 
1     Jan 13  a2

Set 2
ID    Date    Col2 
1     Jan 11  b1 
1     Jan 15  b2

Set 3
ID    Date    Col3
1     Jan 15  c1 
1     Jan 17  c2

Combined Set
ID    Date    Col1    Col2    Col3
1     Jan 11  a1      b1
1     Jan 13  a2
1     Jan 15          b2       c1
1     Jan 17                   c2       

I think a full outer join is able to do this but I am running into major cross product issues.

Answer 1

Give this a try:

select coalesce(t1.date, t2.date, t3.date) date, col1, col2, col3 from table1 t1
full outer join table2 t2 on (t1.date = t2.date)
full outer join table3 t3 on (t2.date = t3.date)