How to group same table differently in outer query and subquery - mysql

Question

Table looks like this:
id | number | provider| datetime | keyword|country|
1 | 1 | Mobitel |2012-11-05| JAM | RS |
2 | 2 | Telekom |2013-04-25| ASTRO| RS |
3 | 1 | Si.Mobil|2013-04-27| DOMACE| BA |
4 | 4 | Telenor |2013-04-21| BIP | HR |
5 | 7 | VIP |2013-04-18| WIN | CZ |
6 | 13 | VIP |2014-05-21| DOMACE| RS |
7 | 5 | VIP |2014-06-04| WIN | HU |
I need to sum all numbers grouped by keyword and country and to sum all numbers again grouped by keyword, country and provider all in one query.
Here is how I tried to do it:
SELECT (SELECT SUM(number),country, keyword
FROM daily_subscriptions
WHERE datetime >= '2016-02-01 23:59:59'
GROUP BY country, keyword )
num_of_all_subs,
SUM(number) as num_of_subs,
country,
keyword,
provider
FROM daily_subscriptions
WHERE datetime >= '2016-02-01 23:59:59'
GROUP BY country, keyword, provider
But this query throws an error:
#1241 - Operand should contain 1 column(s)
Here is what I expect to get:
id | num_of_all_subs|num_of_subs | provider| datetime | keyword|country|
1 | 19 | 4 | Mobitel |2012-11-05| JAM | RS |
2 | 12 | 5 |Telekom |2013-04-25| ASTRO| RS |
3 | 18 | 1 |Si.Mobil |2013-04-27| DOMACE| BA |
4 | 42 | 21 |Telenor |2013-04-21| BIP | HR |
5 | 76 | 23 |VIP |2013-04-18| WIN | CZ |
6 | 13 | 3 |VIP |2014-05-21| DOMACE| RS |
7 | 53 | 11 |VIP |2014-06-04| WIN | HU |
Field num_of_all_subs meaning that sum of all numbers for lets say JAM(keyword) and RS(country) is 19 , but per Mobitel(provider) is num_of_subs 4 from all 19, since there are other providers for that country and keyword(even though they are not displayed in table schema).
Please help me to extract this data, since I'm stuck.

Answer 1

Your subquery for num_of_all_subs (which is a single number) must only return one column and, next problem, one row. Also, this subquery will be evaluated before you group, while you actually want to first group and get the columns num_of_subs, country, keyword and provider, and, afterwards, add another column num_of_all_subs to that first resultset.
You can do this exactly as just described: first get the grouped subquery (here called details), then use a dependent subquery to get, for each row in that subquery, the value for num_of_all_subs by looking at the table (again) and sum over all rows that have the same provider and country:
SELECT
(SELECT SUM(number)
FROM daily_subscriptions ds
WHERE datetime >= '2016-02-01 23:59:59'
and ds.country = details.country
and ds.keyword = details.keyword
) as num_of_all_subs,
details.*
from
(select
SUM(number) as num_of_subs,
country,
keyword,
provider
FROM daily_subscriptions
WHERE datetime >= '2016-02-01 23:59:59'
GROUP BY country, keyword, provider
) as details;
An alternative would be to do calculate both groups seperately, one including provider (details), and one without (all_subs). One will contain num_of_subs, one will contain num_of_all_subs. The you can combine (join) these two queries when they have the same country and keyword:
SELECT
all_subs.num_of_all_subs,
details.*
from
(select
SUM(number) as num_of_subs,
country,
keyword,
provider
FROM daily_subscriptions
WHERE datetime >= '2016-02-01 23:59:59'
GROUP BY country, keyword, provider
) as details
left join
(SELECT
SUM(number) as num_of_all_subs,
country,
keyword
FROM daily_subscriptions
WHERE datetime >= '2016-02-01 23:59:59'
GROUP BY country, keyword
) as all_subs
on all_subs.keyword = details.keyword and all_subs.country = details.country;
In your case, you can use a join instead of a left join, because every row in the first subquery will have a row in the second subquery, although it's usually the safer way do keep it.
While in theory, MySQL could execute these queries identically (and for less complicated queries, it will actually optimize and treat, whenever possible and useful, dependent subqueries like joins), in current MySQL versions this will most likely not be the case and the 2nd option is probably faster. Anyway, for both versions, a composite index on (country, keyword, provider) will do wonders.