Reference a view inside of the view in postgresql - sql

Question

I would like to do something like the following:
CREATE VIEW foo_view AS
SELECT
foo.id,
foo.carryover_id,
foo.amount,
(SELECT SUM(foo_view.total)
FROM foo_view
WHERE foo_view.carryover_id = foo.id
) AS carryover_amount,
(amount + carryover_amount) AS total;
However, this raises an error relation "foo_view" does not exist. I would think that RECURSIVE would come in handy here, but the documentation is more reference than tutorial and there don't seem to be any resources out there to help me. Thoughts?
EDIT
Here's a sqlfiddle with a relevant schema http://sqlfiddle.com/#!15/6834d/1

Answer 1

You are right, your article is what you needed.
I formatted the data first into a fooBar temp table:
SELECT b.id
, foo_id
, ISNULL(f.carryover_id, foo_id) as carryover_id
, b.amount
, ROW_NUMBER() OVER(
PARTITION BY ISNULL(f.carryover_id, foo_id)
ORDER BY b.id asc) as rowNmbr
INTO #fooBar
FROM #bar as b
INNER JOIN #foo as f
ON b.foo_id = f.id;
The first row in the WITH is the top level. Then it recursively goes through each level. The rowNmbr is the level.
WITH summarizedFoo(rowNmbr, id, foo_id, carryover_id, amount, totalAmount)
AS
(
SELECT f.rowNmbr
, f.id
, f.foo_id
, f.carryover_id
, ISNULL(f.amount,0) as amount
, ISNULL(f.amount,0) as totalAmount
FROM #fooBar as f
WHERE f.rowNmbr = 1
UNION ALL
SELECT f.rowNmbr
, f.id
, f.foo_id
, f.carryover_id
, ISNULL(f.amount,0) as amount
, CAST((ISNULL(f.amount,0)
+ ISNULL(s.totalAmount,0)) as decimal) as totalAmount
FROM #fooBar as f
INNER JOIN summarizedFoo as s
ON f.carryover_id = s.carryover_id
AND f.rowNmbr = s.rowNmbr +1
)
SELECT rowNmbr, id, foo_id, carryover_id, amount, totalAmount
FROM summarizedFoo
I did this in T-SQL, but to make this work in your fiddler
Here is the PostgreSQL version:
Create a fooBar table (could be a view):
INSERT INTO fooBar
SELECT CAST(b.id as INTEGER)
, CAST(foo_id as INTEGER)
, CAST(CASE WHEN f.carryover_id is NULL THEN foo_id ELSE f.carryover_id END as INTEGER) as carryover_id
, CAST(b.amount as DECIMAL)
, CAST(ROW_NUMBER() OVER(PARTITION BY CASE WHEN f.carryover_id is NULL THEN foo_id ELSE f.carryover_id END ORDER BY b.id asc) as INTEGER) as rowNmbr
FROM bar as b
INNER JOIN foo as f
ON b.foo_id = f.id;
Here is the WITH RECURSIVE:
WITH RECURSIVE summarizedFoo(rowNmbr, id, foo_id, carryover_id, amount, totalAmount)
AS
(
SELECT f.rowNmbr, f.id, f.foo_id, f.carryover_id
, f.amount
, f.amount
FROM fooBar as f
WHERE f.rowNmbr = 1
UNION ALL
SELECT f.rowNmbr, f.id, f.foo_id, f.carryover_id
, f.amount
, f.amount + s.totalAmount
FROM fooBar as f
INNER JOIN summarizedFoo as s
ON f.carryover_id = s.carryover_id
AND f.rowNmbr = s.rowNmbr +1
)
SELECT rowNmbr, id, foo_id, carryover_id, amount, totalAmount
FROM summarizedFoo
I tested in SSMS(T-SQL version) and Fiddler(PostgreSQL), and verified the results in Excel.
Here is Fiddler of the solution:
http://sqlfiddle.com/#!15/a7822/3

Answer 2

The trick is to populate a table with source > target pairs, then to use that table to calculate the total amount:
CREATE RECURSIVE VIEW leaf_view(target_id, source_id) AS (
SELECT id, id FROM foo
UNION ALL
SELECT leaf_view.target_id, foo.id
FROM leaf_view
JOIN foo ON foo.carryover_id = leaf_view.source_id
);
CREATE VIEW foo_view(id, total) AS
SELECT leaf_view.target_id, SUM(bar.amount)
FROM leaf_view
LEFT JOIN bar ON leaf_view.source_id = bar.foo_id
GROUP BY leaf_view.target_id;
http://sqlfiddle.com/#!15/6834d/62
I owe this answer to RhodiumToad in #postgresql on freenode. Note that this will have problems for large foo since the optimizer generally can't work on recursive queries.

Answer 3

It looks like you want to have a cumulative running total amount. You could get this with a self-join, or a sub query, e.g:
select
id,
amount,
(select sum amount from foo b where b.id <= a.id ) as cumulative
from foo a
or
select
a.id,
a.amount,
sum(b.amount) as cumulative
from foo a
join foo b on b.id <= a.id
group by a.id, a.amount

Answer 4

Editing my answer as below.. I realized you are trying to do something recursive, does this help?? It'd really help if you gave a sample input and the output that you are expecting..
WITH RECURSIVE foo_view(id, total) AS (
SELECT id, amount from foo;
UNION ALL
SELECT foo_view.id, sum(foo_view.total+foo.amount)
FROM foo
JOIN
foo_view
ON
foo_view.id = foo.carryover_id
)
SELECT * from foo_view