Left Join and Sum - mysql

Question

I have two tables, one that lists grants/loans and one that lists individual expenditures. They share an ID column as each expenditure is assigned to a specific grant or loan. I'm trying to use LEFT JOIN to sum the expenditures for all the loans combined, but not the grants.
Here's where I'm at:
SELECT SUM(expenses.total_amt) AS total
FROM expenses WHERE loans_grants.grant_loan_type = 'Loan'
LEFT JOIN loans_grants
ON expenses.grant_loan_id = loans_grants.internal_id;
Any tips much appreciated!
Edit: thanks all, and apologies for the half baked question, it was late and I was in the weeds.
Here's the basic structures:
expenses:
expenses table structure
loans_grants:
loans_grants table structure
I've updated the code based on #jwood74's answer to this:
SELECT l.internal_id, SUM(e.total_amt) amount
FROM loans_grants l
LEFT JOIN expenses e ON e.grant_loan_id = l.internal_id
WHERE grant_loan_type = 'Loan'
group by l.internal_id
which produces this:
internal id
amount
1
3234
4
null
5
7625
7
null
9
null
Please excuse my noviceness, but I'm trying to sum up all expenses for loans, so I'd like to return 3234 + 7625, rather than summing expenses for each loan separately. Thanks for your help!

Answer 1

If you are looking for a SINGLE ROW RETURNED, you do not need to do a group by anything... just the SUM() of what you are looking for.
Second, do not post pictures of your sample data and table structures. Edit your original post and type the values in, even if you copy/paste the data and format it for readability (via Ctrl+K, or the curly brackets {} icon above post editing header area).
In this case, your tables
Loan_Grants table
Internal_id grant_loan_type
1 Loan
2 Grant
3 Grant
4 Loan
5 Loan
6 Grant
7 Loan
8 Grant
9 Loan
Expenses Table
total_amt grant_loan_id
2000 1
245 5
4500 5
2200 5
445 5
185 5
1234 1
50 5
Starting with your Loan_Grants table filtered on just your 'Loan' records
select
sum( e.total_amt ) totalExpenses
from
loan_grants lg
JOIN expenses e
on lg.internal_id = e.grant_loan_id
where
lg.grant_loan_type = 'Loan'
You dont want a left-join unless you explicitly want to see ALL "Loan" entries, even if they have no expenses yet recorded. By doing a regular (inner) JOIN, it means there MUST be a record in the expenses table. Again, based on your needs. If you have 10,000 loans and only 247 loans have expenses, do you want to see all 10,000 or just the 247 and what their totals are. Since you are summarizing to a single return record, JOIN is your best choice here.
For future, ALWAYS try to apply a table.column or alias.column to all your fields so anyone assisting does not have to guess which table the column comes from.

Answer 2

Without knowing the exact format of the two tables, it's a bit hard. But here would be the general idea-
select
l.id,
sum(e.amount) amount
from loans_grants l
left join expenses e on e.grant_loan_id = l.internal_id
where grant_loan_type = 'Loan'
group by l.id