JPA中两个不同实体的值总和

Question

I have two sums to calculate in JPA, from two different entities:

SELECT SUM(da.debtorBalance) FROM DebtorAccount da WHERE <conditions for DebtorAccounts>

and

SELECT SUM(mda.debtorBalance) FROM MasterDebtorAccount mda WHERE <conditions for MasterDebtorAccounts>

What I need is sum of this sums. Is it possible by JPAQL? Or I need to run two separate queries and add this in the application?

Answer 1

You can't in strict JPQL.

In SQL, it would be something like

SELECT SUM(a) FROM (SELECT da.debtorBalance a from DebtorAccount UNION SELECT mda.debtorBalance a FROM MasterDebtorAccount)

JPA does not support UNION, although several implementations do.

And no, you can't do this without union because relational algebra means that you begin with DebtorAccount * MasterDebtorBalance and after that you refine it through conditions / aplying functions.

Answer 2

have you tried?

SELECT SUM(SUM(da.debtorBalance), SUM(mda.debtorBalance)) 
FROM DebtorAccount da, MasterDebtorAccount mda
WHERE (<conditions for DebtorAccounts>) OR (<conditions for MasterDebtorAccounts>)

Regadrs,