Question

When I run the below query:

select SUM(t1.total_amount) as one, SUM(t2.total_amount) as two
from table1 t1, table2 t2;

I get these results:

ONE     TWO
2000    3000

But when I run this query:

select SUM(t1.total_amount) as one table1 t1;

I get this result:

ONE
50

It looks like the result from the first query is incorrect. Can anybody point me to the right direction?

Answer 1

When doing this:

select * from table1 t1, table2 t2

you’re actually cross joining both tables, resulting in a cartesian product (every row in t1 is combined with every row in t2).

You’re probably missing a JOIN condition:

select sum(t1.total_amount), sum(t2.total_amount)
from t1 join t2 on t1.[???] = t2.[???]

EDIT:

based on your comment, it looks like you want a union of these two separate queries
select ‘t1’, sum(total_amount) from t1
union
select ‘t2’, sum(total_amount) from t2

This will show the sums in two rows instead of columns, but it’s the easiest way AFAIK.