Scenes
Different types of data need to be counted and displayed as horizontal data.
For example:
Statistics the sales of different types of products of the company.
solution
At first I saw a bit of a cloud. It's actually very simple, just use if or case.
Solve directly in sql
select
sum(
case category
when 'Alcohol' then amount
end
) as AlcoholAmount,
sum(
case category
when 'smoke' then amount
end
) as SmokeAmount
from sales
where company='a-company'
group by category
The returned field directly corresponds to the value, which can be received by the entity class.
Return to the list and process in the code
select
category,sum(amount) as totalAmount
from sales
where company='a-company'
group by category
In this way, a map can be returned and then traversed in java. It is also possible to put it into the entity class according to the type.