problem with join

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От Edward W. Rouse
Тема problem with join
Дата
Msg-id 003d01c75086$829326b0$143c520a@ntc2s.comsquared.com
обсуждение исходный текст
Ответы Re: problem with join  (Bruno Wolff III <bruno@wolff.to>)
Список pgsql-sql
I have 2 tables that look like this:
 
table1              table2
-----------------   ------------------------
value1 | value2     value1 | value3 | value4
-----------------   ------------------------
one    | a          one    | a      | jim
one    | b          one    | d      | bob
one    | c          two    | d      | bill
many   | d          two    | f      | sue
many   | e          three  | d      | mary
some   | f          three  | f      | jane
 
my query is like this:
 
select b.value1, value2, count(value4)
from table1 as a join table2 as b on (a.value2 = b.value3)
where (a.value1 in ('one', 'two', 'three', 'many') or a.value2 = 'f')
and b.value1 in ('one', 'two', 'three')
group by b.value1, value2
order by b.value1, value2;
 
I get back correct results EXCEPT I don't get back empty counts.
 
The results that I need from the tables above should look like this:
 
one, a, 1
one, b, 0
one, c, 0
one, d, 1
one, e, 0
one, f, 0
two, d, 1
two, e, 0
two, f, 1
three, d, 1
three, e, 0
three, f, 1
 
What I get are all of the rows with counts, but none of the rows where
the count would be 0. I understand why this query works that way, but I
need to find away to resolve the many to one relations that are
backwards in this case. Can anyone come up with a query that will
include the results that have counts of 0?
 
I tried using coalesce(count(value4)) and case count(value4) = 0
with no luck. I tried left and right joins and the right join gave me
the same results while the left join gave me rows like:
 
many, d, 3
 
I'm beginning to wonder if this is even possible.
 
 
 
Ed

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