[GENERAL] Different result depending on order of joins

[Nicklas Avén]

Hallo


I was a little surprised by this behavior.
Is this what is supposed to happen?


This query returns what I want:



with
a as (select generate_series(1,3) a_val)
,b as (select generate_series(1,2) b_val)
,c as (select generate_series(1,1) c_val)
select * from a 
inner join c on a.a_val=c.c_val
full join b on a.a_val=b.b_val
;


I get all values from b since it only has a full join and nothing else.


But if I change the order in the joining like this:



with 
a as (select generate_series(1,3) a_val)
,b as (select generate_series(1,2) b_val)
, c as (select generate_series(1,1) c_val)
select * from a 
full join b on a.a_val=b.b_val
inner join c on a.a_val=c.c_val
;


also b is limited to only return value 1.


I thought that the join was defined by "on a.a_val=c.c_val"
and that the relation between b and the rest wasn't affected by that last inner 
join.


I use PostgreSQL 9.3.6


Is this the expected behavior?


Thanks


Nicklas Avén