Re: counting related rows

>>>>> "FB" == Frank Bax <fbax(at)sympatico(dot)ca> writes:

FB> It would help if you provided:
FB> a) statements to create sample data
FB> b) expected results from sample data

FB> Does this do what you want?

FB> select * from m, (SELECT count(*) AS nch FROM m WHERE o = (SELECT o
FB> FROM m WHERE id=30016) AND name ILIKE (SELECT name || '/%' FROM m
FB> WHERE id=30016)) om;

That is almost right, except that it uses id=30016's nch value for every
row in the result, rather than computing each row's own nch.

As an example:

create TABLE m ( id integer primary key, o integer, name text,
f1 integer, f2 integer, f3 integer);

insert into m values (1, 3, 'a', 0, 1, 1);
insert into m values (2, 3, 'a/short', 1, 0, 1);
insert into m values (3, 3, 'a/short/path', 1, 0, 0);
insert into m values (4, 4, 'nothing', 0, 0, 1);
insert into m values (5, 2, 'nothing', 0, 1, 0);
insert into m values (6, 2, 'nothing/of', 1, 0, 0);
insert into m values (7, 2, 'nothing/of/value', 0, 0, 0);

The select should result in something like:

id | o | name | f1 | f2 | f3 | nch
----+---+------------------+----+----+----+-----
1 | 3 | a | 0 | 1 | 1 | 2
2 | 3 | a/short | 1 | 0 | 1 | 1
3 | 3 | a/short/path | 1 | 0 | 0 | 0
4 | 4 | nothing | 0 | 0 | 1 | 0
5 | 2 | nothing | 0 | 1 | 0 | 2
6 | 2 | nothing/of | 1 | 0 | 0 | 1
7 | 2 | nothing/of/value | 0 | 0 | 0 | 0

since rows 2 and 3 are children of row 1, row 3 is also a child of
row 2, rows 6 and 7 are children of row 5 and row 7 is also a child
of row 6.

-JimC
--
James Cloos <cloos(at)jhcloos(dot)com> OpenPGP: 1024D/ED7DAEA6