SQL add a column with COUNT(*) to my query - sql

Question

I need to add a column with the content of this query :
SELECT COUNT(*) FROM account_subscriptiongroups WHERE account_subscriptiongroups.active = true AND account_subscriptiongroups.user_id = account_user.id
to this query :
SELECT
account_user.id as user_id, account_user.email, account_user.first_name, account_user.last_name, account_user.phone,
account_subscriptiongroup.id as sub_group_id,
account_adminaction.description,
account_adminaction.id as admin_action_id,
account_adminaction.created_on as subscription_ended_on
FROM
account_adminaction
LEFT JOIN
account_user ON account_user.id = account_adminaction.user_id
LEFT JOIN
account_subscriptiongroup ON account_adminaction.sub_group_id = account_subscriptiongroup.id
WHERE
account_adminaction.created_on >= '2021-04-07' AND account_adminaction.created_on <= '2021-04-13' AND
((account_adminaction.description LIKE 'Arrêt de l''abonnement%') OR (account_adminaction.description LIKE 'L''utilisateur a arrêté%'))
ORDER BY
subscription_ended_on
I tried adding a LEFT JOIN like that:
LEFT JOIN
account_subscriptiongroup all_sg ON account_user.id = account_subscriptiongroup.user_id
with this line in my WHERE statement :
AND all_sg.active = true
and this line in my SELECT :
COUNT(all_sg.id)
but I get an error :
ERROR: column "account_user.id" must appear in the GROUP BY clause or be used in an aggregate function
LINE 2: account_user.id as user_id, account_user.email, account_us...
^
I don't understand how I could perform this action properly

Answer 1

To count something, you need to specify a group where that count applies.
So every column that you select (and is not used in an aggregate function, like COUNT or SUM), you need to mention in the GROUP BY clause.
Or to put it the other way around: the non-aggregate columns must apply to all rows that are contained in that particular COUNT.
So between the WHERE and ORDER BY clauses, add a GROUP BY clause:
GROUP BY account_user.id, account_user.email, account_user.first_name, account_user.last_name, account_user.phone,
account_subscriptiongroup.id,
account_adminaction.description,
account_adminaction.id,
account_adminaction.created_on
If, on the other hand, you want a count from a different table, you can add a sub-select:
SELECT
account_user.id as user_id, account_user.email, account_user.first_name, account_user.last_name, account_user.phone,
account_subscriptiongroup.id as sub_group_id,
account_adminaction.description,
account_adminaction.id as admin_action_id,
account_adminaction.created_on as subscription_ended_on,
(SELECT COUNT(*)
FROM account_subscriptiongroups
WHERE account_subscriptiongroups.active = true
AND account_subscriptiongroups.user_id = account_user.id) AS groupcount
FROM
account_adminaction
LEFT JOIN
account_user ON account_user.id = account_adminaction.user_id

Answer 2

You can left join to to a derived table that does the grouping and counting:
SELECT au.id as user_id, au.email, au.first_name, au.last_name, au.phone,
asg.id as sub_group_id,
ad.description,
ad.id as admin_action_id,
ad.created_on as subscription_ended_on,
asgc.num_groups
FROM account_adminaction ad
LEFT JOIN account_user au ON au.id = ad.user_id
LEFT JOIN account_subscriptiongroups asg on ON ad.sub_group_id = asg.id
LEFT JOIN (
SELECT user_id, count(*) as num_groups
FROM account_subscriptiongroups ag
WHERE ag.active
GROUP by user_id
) asgc on asgc.user_id = au.id
WHERE ad.created_on >= '2021-04-07'
AND ad.created_on <= '2021-04-13'
AND ((ad.description LIKE 'Arrêt de l''abonnement%') OR (ad.description LIKE 'L''utilisateur a arrêté%'))
ORDER BY subscription_ended_on
It's not entirely clear to me, what you are trying to count, but another option (most probably slower) could be to use a window function combined with a filter clause:
count(*) filter (where asg.active) over (partition by asg.user_id) as num_groups

Answer 3

EDIT: my answer is the same as submitted by a_horse_with_no_name
Two answers, a literal one just solving the problem you posed, and then another one questioning whether what you asked for is really what you want.
Simple answer: modify your desired query to add user_id to the Select and remove user_id from the Where clause. Now you have a table that can be left-joined to the rest of your larger query.
...
Left Join (Select user_id, count(*) as total_count
From account_subscriptiongroup
Where account_subscriptiongroups.active = true
Group By user_id) Z
On Z.user_id=account_user.id
I question whether this count is what you really want here. This counts every account_subscriptiongroup entry for all time but only the active ones. Your larger query brings back inactive as well as active records, so if your goal is to create a denominator for a percentage, you are mixing 'apples and oranges' here.
If you decide you want a total by user of the records in your query instead, then you can add one more element to your larger query without adding any more tables. Use a windowing function like this:
Select ..., Sum(Case When account_subscriptiongroup.active Then 1 else 0 End) Over (Group By account_user.id) as total count
This just counts the records within the date range and having the desired actions.