SQL subquery to fetch rows by column values - mysql

Question

I have a PostgreSQL table like this:
CREATE TABLE foo(man_id, subgroup, power, grp)
AS VALUES
(1, 'Sub_A', 4, 'Group_A'),
(2, 'Sub_B', -1, 'Group_A'),
(3, 'Sub_A', -1, 'Group_B'),
(4, 'Sub_B', 6, 'Group_B'),
(5, 'Sub_A', 5, 'Group_A'),
(6, 'Sub_B', 1, 'Group_A'),
(7, 'Sub_A', -1, 'Group_B'),
(8, 'Sub_B', 2, 'Group_B'),
(9, 'Sub_C', 2, 'Group_B');
The power calculation works like this:
Total Power of Subgroup Sub_A in the grp Group_A is (4 + 5 ) = 9
Total Power of Subgroup Sub_B in the grp Group_A is ((-1) + 1 ) = 0
Total Power of Subgroup Sub_A in the grp Group_B is ((-1) + (-1) ) = -2
Total Power of Subgroup Sub_B in the grp Group_B is (6 + 2 ) = 8
So the power of Sub_A in the Group_A is not equal to power of Sub_A in the Group_B
So the power of Sub_B in the Group_A is not equal to power of Sub_B in the Group_B
I want to query the database and fetch the rows where, for a same subgroup name total power is not equal across all the other grp names.
What would be the recommended way to do this?
I can find the sum of total power:
SELECT sum(power) AS total_power
FROM foo
GROUP BY grp
MySQL solution will be accepted as well.

Answer 1

One way:
SELECT f.*
FROM (
SELECT subgroup
FROM (
SELECT subgroup, grp, sum(power) AS total_power
FROM foo
GROUP BY subgroup, grp
) sub
GROUP BY 1
HAVING min(total_power) <> max(total_power) -- can fail for NULL values;
) sg
JOIN foo f USING (subgroup);
In your example all rows qualify except for the last one with 'Sub_C'.
Closely related to your previous question:
Do all groups have equal total power for given subgroup?
Similar explanation and considerations.
db<>fiddle here

Answer 2

I think a way to phrase your problem is that you want to total the power for subgroup in a group, then find if a subgroup with the same name exists in another group with a different power.
The first step is to total the powers like you want:
SELECT grp, subgroup, sum(power) as power
FROM foo
GROUP BY grp, subgroup
That should give you a result like:
grp subgroup power
------- -------- -----
Group_A Sub_A 9
Group_A Sub_B 0
Group_B Sub_A -2
Group_B Sub_B 8
Group_B Sub_C 2
Once you have that, you can use a CTE to join the results with itself for the comparison to get what you want. You don't specify whether you want Sub_C to appear, if 'not existing' qualifies as having a 'different total power', then you would want to use a left join and check for nulls in alias b. The < in the join makes it so that each difference only appears once with the lower order group as grp1.
WITH totals AS (
SELECT grp, subgroup, sum(power) as power
FROM foo
GROUP BY grp, subgroup
ORDER BY grp, subgroup
)
SELECT a.subgroup,
a.grp as grp1, a.power as Power1,
b.grp as grp2, b.power as Power2
FROM totals a
INNER JOIN totals b ON b.subgroup = a.subgroup
and a.grp < b.grp
WHERE b.power <> a.power
ORDER BY a.subgroup, a.grp, b.grp

Answer 3

with totals as (
select grp, subgroup, sum(power) as total_power
from foo
group by grp, subgroup
)
select * from totals t1
where t1.total_power <> all (
select t2.total_power from totals t2
where t2.subgroup = t.subgroup and t2.grp <> t1.grp
)
or
with totals as (
select grp, subgroup, sum(power) as total_power
from foo
group by grp, subgroup
), matches as (
select grp, subgroup, count(*) over (partition by subgroup, total_power) as matches
)
select * from counts where matches = 1;

Answer 4

I would use window functions:
select f.*
from (select f.*,
min(sum_value)) over (partition by group) as min_sum_value,
max(sum_value)) over (partition by group) as max_sum_value,
from (select f.*,
sum(value) over (partition by subgroup, group) as sum_value
from foo f
) f
) f
where min_sum_value <> max_sum_value;