How to calculate sum of two columns from two different tables without where clause?

Question

I am using the following sql statement to sum values from two columns from two different tables. The statement can output but not the desired result.

SELECT
         


        

Answer 1

This should do it:

select income, expense, income-expense balance
from (select sum(rate) income
      from _income) i
JOIN (select sum(rate) expense
      from _expense) e