Unexpected LEFT JOIN behavior with condition in ON clause - mysql

Question

I have the following three tables:
fees - has information about a fee on a bill
payments - has information about payments on a bill (including payments to fees)
details - has detailed information about the payment
I'm struggling to understand why my query isn't returning the result I expect.
SQL Fiddle: sqlfiddle.com/#!9/942636/3
CREATE TABLE fees (
receipt_number int(11) NOT NULL,
bill_number int(11) NOT NULL,
version int(11) NOT NULL,
fee_id int(11) NOT NULL,
fee_type varchar(30) NOT NULL
);
CREATE TABLE payments (
receipt_number int(11) NOT NULL,
bill_number int(11) NOT NULL,
version int(11) NOT NULL,
payment_id int(11) NOT NULL,
amount decimal(13,2) NOT NULL DEFAULT '0.00'
);
CREATE TABLE details (
receipt_number int(11) NOT NULL,
payment_id int(11) NOT NULL,
fee_type varchar(30) DEFAULT NULL
amount decimal(13,2) NOT NULL DEFAULT '0.00'
);
INSERT INTO fees (receipt_number, bill_number, version, fee_id, fee_type)
VALUES (111, 100, 1, 1, 'a'),
(111, 100, 1, 1, 'b'),
(111, 100, 1, 2, 'c'),
(111, 100, 1, 2, 'd');
INSERT INTO payments (receipt_number, bill_number, version, payment_id, amount)
VALUES (111, 100, 1, 98, 30.00),
(111, 100, 1, 99, 60.00);
INSERT INTO details (receipt_number, payment_id, fee_type, amount)
VALUES (111, 98, 'a', 10.00),
(111, 98, 'b', 10.00),
(111, 98, 'd', 10.00),
(111, 99, 'a', 20.00),
(111, 99, 'b', 20.00),
(111, 99, 'c', 20.00);
I'm attempting to find out if:
A bill has a fee with type 'c'
There is a payment made towards that fee (determined by the fee_type)
My query:
SELECT fees.bill_number, details.receipt_number AS has_payment_type_c
FROM fees
LEFT JOIN payments
USING (bill_number, version)
LEFT JOIN details
ON details.receipt_number = payments.receipt_number
AND details.payment_id = payments.payment_id
AND details.fee_type = 'c'
WHERE fees.fee_type = 'c'
AND details.receipt_number IS NULL;
I get the result:
bill_number has_payment_type_c
100 (null)
I should not see the bill_number in this list, as the bill has a fee and a payment towards that fee.
I am filtering the details.fee_type in the ON clause to both reduce the number of records looked up in that table and to only join to that table for that specific fee_type. The query seems to "work" (0 results) by moving the fee_type join condition to the WHERE clause, but I don't think that is correct.
My questions:
What am I doing wrong in my query? How can I fix it to produce the result I'm looking for, and how does that fix work?
Assuming I get a working query, can I just simply reverse the table order and the SELECT to find the opposite information - payments of a certain fee_type without an associated fee record of that same type?

Answer 1

The answer is to use a derived table that inner joins payments and details, and then left join the derived table to fees:
SELECT DISTINCT fees.bill_number, fees.version, x.bill_number AS has_payment_type_c
FROM fees
LEFT JOIN (
SELECT payments.bill_number, payments.version, details.fee_type
FROM payments
JOIN details
USING(receipt_number, payment_id)
WHERE details.fee_type = 'c'
) x
ON fees.bill_number = x.bill_number
AND fees.version = x.version
WHERE fees.fee_type = 'c'
AND x.bill_number IS NULL;
This will return the expected 0 results, and can be validated by removing the where condition that checks for a null x.bill_number:
bill_number version has_payment_type_c
100 1 100
The same approach works for finding payments without a fee. Use a derived table that inner joins payments and details, then left join to fees. SELECT the fee.bill_number AS has_payment_type_c and add WHERE fee.bill_number IS NULL to the WHERE clause.