Spring Data, JPQL, Group by month of a date column(type LocalDate) - postgresql

Question

I have to get total price in month from a date yy-mm-dd with jpql query but I can't do it.
#Query(value = "select new com.talan.food.dto.MonthIncomes( function('date_format',date,'%Y-%m'),SUM(p.price)) from Reservation p group by function('date_format',p.date,'%Y-%m')" )
public List<MonthIncomes> getIncomeByMonth();
And in the table of entity I have:
public class Reservation {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private double price;
#ManyToOne #JoinColumn(name="userId" )
public User user;
private LocalDate date;
private boolean confirmed;
}
And I will put the result in the class :
public class MonthIncomes {
private LocalDate date ;
private double price;
public MonthIncomes (LocalDate date, double price) {
this. date= date;
this.price = price;
}
}

Answer 1

You could something like this in your query
SELECT p.date as date ,
SUM(p.price) as price
FROM reservation p
WHERE p.date >= '2022-01-01'
GROUP BY
EXTRACT(month from p.date)
depending on the amount of yours you have to go back you would have to change the extract statement a bit. Nevertheless your problem looks like something that you could approach with the extract function
https://www.postgresqltutorial.com/postgresql-date-functions/postgresql-extract/

Answer 2

i resolve the problem by using this syntaxe:
#Query(value = "select new com.food.dto.MonthIncomes(EXTRACT(month from p.date),SUM(p.price)) from Reservation p group by EXTRACT(month from p.date) ORDER BY EXTRACT(month from p.date)")
public List<MonthIncomes> getIncomeByMonth();