sqlite multiple query conditions - sqlite

Question

I've searched but can't find the right answer, and I'm going round in circles.
I have
CREATE TABLE History (yr Int, output Int, cat Text);
yr output cat
---------- ---------- ----------
2015 10 a
2016 20 a
2017 30 a
2018 50 a
2019 70 a
2015 100 b
2016 200 b
2017 300 b
2018 500 b
2019 700 b
2015 1000 c
2016 2000 c
2017 3000 c
2018 5000 c
2019 7000 c
2015 10000 d
2016 20000 d
2017 30000 d
2018 50000 d
2019 70000 d
I've created two views
CREATE VIEW Core AS select * from History where cat = "c" or cat = "d";
CREATE VIEW Plus AS select * from History where cat = "a" or cat = "b";
My query is
select distinct yr, sum(output), (select sum(output) from core group by yr) as _core, (select sum(output) from plus group by yr) as _plus from history group by yr;
yr sum(output) _core _plus
---------- ----------- ---------- ----------
2015 11110 11000 110
2016 22220 11000 110
2017 33330 11000 110
2018 55550 11000 110
2019 77770 11000 110
Each of the individual queries works but _core and _plus columns are wrong when it's all put together. How should I approach this please.

Answer 1

You may generate your expected output without a view, using a single query with conditional aggregation:
SELECT
yr,
SUM(output) AS sum_output,
SUM(CASE WHEN cat IN ('c', 'd') THEN output ELSE 0 END) AS _core,
SUM(CASE WHEN cat IN ('a', 'b') THEN output ELSE 0 END) AS _plus
FROM History
GROUP BY
yr;
If you really wanted to make your current approach work, one way would be to just join the two views by year. But that would leave open the possibility that each view might not have every year present.