Propel 1.6 Greatest n per group - greatest-n-per-group

Question

I need to build propel query that can get the latest purchase of client
Please use these table/column names in your answer:
customer: id, name
purchase: id, customer_id, date
from this question here SQL join: selecting the last records in a one-to-many relationship
I need to build propel query based one of these queries:
SELECT c.*, p1.*
FROM customer c
JOIN purchase p1 ON (c.id = p1.customer_id)
LEFT OUTER JOIN purchase p2 ON (c.id = p2.customer_id AND
(p1.date < p2.date OR p1.date = p2.date AND p1.id < p2.id))
WHERE p2.id IS NULL;
or
SELECT c.*, p.*
FROM customer c INNER JOIN
(
SELECT customer_id,
MAX(date) MaxDate
FROM purchase
GROUP BY customer_id
) MaxDates ON c.id = MaxDates.customer_id INNER JOIN
purchase p ON MaxDates.customer_id = p.customer_id
AND MaxDates.MaxDate = p.date

Answer 1

Well, given your question (finding latest purchase for a given client) then you just want to do a search on the purchase table ordering by date and limiting to one:
$lastPurchase = PurchaseQuery::create()
->filterByCustomerId($customerId)
->orderByDate(Criteria::DESC)
->limit(1)
->find();
The answer you link to, however, is finding all customers AND their latest purchase. In that case I would probably use a custom SQL query (although you technically can do this with Propel functions, it would be more difficult and would not get you very much since you won't be hydrating objects (at least, not easily).
UPDATE
Here's some information on doing a manual query. Note that when doing so, the data returned will NOT be Propel objects, but you can do on-demand hydration if needed.
Example:
$sql = "SELECT c.*, p1.*
FROM customer c
JOIN purchase p1 ON (c.id = p1.customer_id)
LEFT OUTER JOIN purchase p2 ON (c.id = p2.customer_id AND
(p1.date < p2.date OR p1.date = p2.date AND p1.id < p2.id))
WHERE p2.id IS NULL;";
$conn = Propel::getConnection(CustomerPeer::DATABASE_NAME);
$stmt = $conn->prepare($query);
if ($stmt->execute()) {
while($result = $stmt->fetch()) {
$someField = $result['...'];
}
}