simple finance database, need some statistics, how to query? - sql

Question

I want to use a simple private cashflow database. Nothing special.
Therefor I use a table "finance_flow", where I can put all my in- and outcomes.
Income -> amount > 0
outcome -> amount < 0
Table structure
table "finance_flow" with example-data
id
category_id
amount
date
note
int
int
float
timestamp
varchar
1
1
+60,00
5.2.23
use for xy
2
2
-10,00
8.2.23
to Tom for school
3
3
-8,96
8.2.23
milk, bread, cheese
table "category"
id
name
1
tips
2
kids
3
shop
Of course there is a correct foreign-key-constraint.
What I want:
I want some statistical data, for example:
-current status of my money
-total outcomes for each category
-procentual values of those would be nice
I know how to get the total current state:
SELECT sum(amount) as total FROM finance_flow
I know how to get the total per category
SELECT abs(sum(amount)) as total_per_cat, category.name
FROM finance_flow
LEFT JOIN category ON financeflow.cat_id = category.id
GROUP BY category_id [WHERE date = 'february']
(Here I use the function abs(x), because I am not interessted in the sign.
The where-clause is optional, I want this, if the basics are correct, for monthly reports.
How to get the procentual values?
Can I get all this stuff with one query? :)
Expected result:
procentual_per_cat = total_per_cut / total_income(february) * 100
where
total_per_cut = abs(sum(amount)) for category x
total_income(february) = 60
resulting table:
name
total_per_cat
procentual_per_cat
kids
10
16.67 %
shop
8.96
14.93 %

Answer 1

Calculating the percentage is the same a dividing by the total amount:
SELECT
abs(sum(amount)) as total_per_cat,
abs(sum(amount))/(select sum(amount) from finance_flow where amount>0) *100 as percentage,
category.name
FROM finance_flow
LEFT JOIN category ON finance_flow.cat_id = category.id
WHERE amount<0
GROUP BY category.name
see: DBFIDDLE