SELECT COUNT(*) GROUP BY out zero rows - sql

Question

Tables in my db:
CREATE TABLE items (
id serial NOT NULL,
user_id integer NOT NULL,
status smallint
);
CREATE TABLE phones (
phone character varying,
users integer[]
);
My Query for find phone numbers where status = 1:
SELECT phones.phone, COUNT(*) AS "count"
FROM phones,items
WHERE phones.phone = ANY (Array['7924445544', '8985545444'])
AND items.user_id = ALL (phones.users) AND items.status = 1
GROUP BY phones.phone;
Query out:
phone | count
------------+------
7924445588 | 3
Need out with ZERO count:
phone | count
------------+-------
8985545444 | 0
7924445544 | 3
How to get that?

Answer 1

It's a bit tricky to create non-existing rows. (There are billions of them, at least...)
Do a UNION ALL with a select providing the result you want if that phone no doesn't exist.
<current query>
UNION ALL
select '8985545444',0
from one_row_table where not exists (select 1 from phones
where phones.phone = '8985545444')
EDIT:
If the phone numbers do exists, but not fulfill the WHERE clause conditions, use a correlated sub-select to do the count:
SELECT phones.phone,
(select count(*) from items
where items.status = 1
and items.user_id = phones.users) as "Count"
FROM phones
WHERE phones.phone = ANY (Array['7924445544', '8985545444'])

Answer 2

You shouldn't do that in the query. However it is rather easy to do it if you want to:
WITH phone_seek AS(
SELECT '8985545444' AS phone
UNION ALL
SELECT '7924445588 '
)
SELECT phone_seek.phone, COUNT(items.id) AS "count"
FROM
phones_seek
JOIN phones
ON phones_seek.phone = phones.phones
CROSS JOIN items
WHERE
items.user_id = ALL (phones.users) AND items.status = 1
GROUP BY phones.phone;

Answer 3

Count is an aggregate function and generally db engines produces count 0 when no row matches the criteria.
The reason why your query produces no results is inclusion of your phones.phone field in db and the group by.
1) A cheap solution to this is select only count(*) as your application
already be knowing the phone number:
SELECT COUNT(*) AS "count"
FROM phones, items
WHERE phones.phone = '8985545444'
AND items.user_id = ALL (phones.users) AND items.status = 1 ;
2) An ideal solution to this would be your application to handle 0 result
returned by db.
3) And if you need db to do all job you may use something like:
SELECT phones.phone, COUNT(*) AS "count"
FROM phones, items
WHERE phones.phone = '8985545444'
AND items.user_id = ALL (phones.users) AND items.status = 1
GROUP BY phones.phone;
UNION ALL
select '8985545444',0
from one_row_table where not exists (select 1 from phones
where phones.phone = '8985545444')

Answer 4

I'm not well versed with PostreSQL's array syntax, but this seems to be a simple outer join:
SELECT phones.phone, COUNT(items.user_id) AS "count"
FROM phones LEFT JOIN items
ON items.user_id = ALL (phones.users)
AND items.status = 1
WHERE phones.phone = ANY (Array['7924445544', '8985545444'])
GROUP BY phones.phone;