mysql left join take rows together - mysql

Question

I have 3 tables: invoice, person and payement.
I want to have a list of invoices with the client name (from person) and the sum of payements and dates of payements(from payement).
First I made these statement
SELECT V.id, V.datum, V.amount, P.name AS 'client',
(SELECT SUM(B.amount) FROM payement AS B WHERE B.invoiceId = V.id) AS 'payed',
(SELECT GROUP_CONCAT(B.datum SEPARATOR ',') FROM payement AS B WHERE B.invoiceId = V.id) AS 'date payement'
FROM invoice AS V
JOIN person AS P ON (V.clientId = P.id)
WHERE YEAR(V.datum) = '2015'
ORDER BY V.datum;
This give what I want (p.e. a transaction of 1000 on 4 sept and one of 2400 on 10 sept), but works very slow when I have a lot of invoices.
+------+-----------+--------+--------+-------+---------------------+
| id | datum | amount | client | payed | date payement |
+------+-----------+--------+--------+-------+---------------------+
| 75 |2015-09-10 | 3400 |Sommers | 3400 |2015-09-04,2015-09-10|
+------+-----------+--------+--------+-------+---------------------+
So I tried another statement.
SELECT V.id, V.datum, V.amount, P.name AS 'client', B.amount AS 'payed', B.datum 'date payement'
FROM invoice AS V
JOIN person AS P ON (V.clientId = P.id)
LEFT JOIN payement AS B ON B.invoiceId = V.id
WHERE YEAR(V.datum) = '2015'
ORDER BY V.datum;
But this give me 2 rows for 1 invoice, when it is payed with 2 transactions.
Can I solve it with SQL, or is it better to solve it in my application (in Java)?

Answer 1

When an invoice has been paid with 2 payments, which details do you wish to use? the first payment or the 2nd?
Assuming that you want the total payment amount and the latest payment date:-
SELECT V.id,
V.datum,
V.amount,
P.name AS 'client',
SUM(B.amount) AS 'payed',
MAX(B.datum) AS 'date payement'
FROM invoice AS V
JOIN person AS P ON (V.clientId = P.id)
LEFT OUTER JOIN payement AS B ON B.invoiceId = V.id
WHERE YEAR(V.datum) = '2015'
GROUP BY V.id,
V.datum,
V.amount,
P.name
ORDER BY V.datum
I don't use phpmyadmin.
mysql> EXPLAIN SELECT V.factuurnr,
-> V.datum,
-> V.somexcl,
-> P.naam AS 'client',
-> SUM(B.bedrag) AS 'payed',
-> GROUP_CONCAT(DATE_FORMAT(B.datum,'%d/%m/%y') SEPARATOR ',') AS 'date payement'
-> FROM verkoop AS V
-> JOIN persoon AS P ON (V.klantId = P.id)
-> LEFT JOIN betaling AS B ON B.docId = V.id
-> WHERE YEAR(V.datum) = '2015' and month(V.datum)=9
-> GROUP BY V.factuurnr,
-> V.datum,
-> V.somexcl,
-> P.naam
-> ORDER BY factuurnr;
+----+-------------+-------+--------+---------------+---------+---------+----------------+------+----------------------------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-------+--------+---------------+---------+---------+----------------+------+----------------------------------------------+
| 1 | SIMPLE | V | ALL | NULL | NULL | NULL | NULL | 1576 | Using where; Using temporary; Using filesort |
| 1 | SIMPLE | P | eq_ref | PRIMARY | PRIMARY | 4 | meta.V.klantId | 1 | Using where |
| 1 | SIMPLE | B | ALL | NULL | NULL | NULL | NULL | 3291 | |
+----+-------------+-------+--------+---------------+---------+---------+----------------+------+----------------------------------------------+
3 rows in set (0.00 sec)