将SQL satement转换为Zend Db_Table_Abstract_Select代码

Question

I'm trying to fetch the latest row for each customer from the table below.

----------------------------------------------------------------------------------
|  id  |  customer_id  |  type   |  type_id  |    notes    |  timestamp   |  uid |
----------------------------------------------------------------------------------
|  1   |       1       |  sales  |     9     |  Note 1...  |  1432781613  |   9  |
|  2   |       2       |  sales  |     9     |  Note 1...  |  1432791204  |   9  |
|  3   |       3       |  sales  |     9     |  Note 1...  |  1432881619  |   9  |
|  4   |       1       |  sales  |     9     |  Note 2...  |  1442771601  |   9  |
|  5   |       1       |  sales  |     9     |  Note 3...  |  1462781617  |   9  |

I have the following code and SQL statement which works...

$type="sales";

$sql =  "
        SELECT cl1.*
        FROM {$this->_name} cl1
        INNER JOIN  (
                    SELECT customer_id, MAX(timestamp) AS lastTimestamp
                    FROM {$this->_name}
                    WHERE type = '{$type}'
                    GROUP BY customer_id
                    ) cl2
        ON cl1.customer_id = cl2.customer_id AND cl1.timestamp = cl2.lastTimestamp
        ";

$stmt = $this->getAdapter()->query($sql);

Which produces...

SELECT cl1.* FROM customer_contactLog cl1 INNER JOIN ( SELECT customer_id, MAX(timestamp) AS lastTimestamp FROM customer_contactLog WHERE type = 'sales' GROUP BY customer_id ) cl2 ON cl1.customer_id = cl2.customer_id AND cl1.timestamp = cl2.lastTimestamp

I have tried to convert this to "the Zend way" as all my other models are written that way but I am struggling. The code I have come up with is...

    $select = $this ->select()
                    ->from      (
                                array('cl1' => $this->_name),
                                array('cl1.*')
                                )
                    ->join  (
                                array('cl2' => $this->_name),
                                "cl2.type = '{$type}'",
                                array('cl2.customer_id', 'MAX(cl2.timestamp) AS lastTimestamp')
                                )
                    ->where     ('cl1.customer_id = ?', 'cl2.customer_id')
                    ->where     ('cl1.timestamp = ?', 'cl2.lastTimestamp');

But this produces...

    SELECT `cl1`.*, `cl2`.`customer_id`, MAX(cl2.timestamp) AS `lastTimestamp` FROM `customer_contactLog` AS `cl1` INNER JOIN `customer_contactLog` AS `cl2` ON cl2.type = 'sales' WHERE (cl1.customer_id = 'cl2.customer_id') AND (cl1.timestamp = 'cl2.lastTimestamp')

Can anyone tell me where I am going wrong?

Thanks

Answer 1

You can use nested selects within Zend DB queries. This is exactly what you need here - create a subselect and then join it in main one.

$maxTimestampSelect = $this->select()
    ->from(
        $this->_name, 
        array('customer_id', 'lastTimestamp' => new Zend_Db_Expr('MAX(timestamp)'))
    )
    ->where('type = ?', $type)
    ->group('customer_id');

$select = $this->select()
    ->from(
        array('cl1' => $this->_name), 
        array('cl1.*')
    )
    ->join(
        array('cl2' => $maxTimestampSelect), 
        'cl1.customer_id = cl2.customer_id AND cl1.timestamp = cl2.lastTimestamp',
        null
    );