Zend_Db_Select for update/delete query's - php

Question

While working on a mapping structure for our applications we ran into some trouble regarding the code consistency. While it's easy to make select query's with the Zend_Db_Select class (with functions like: $select->from('table')->where('id=?,1), it wouldn't work for update/delete query's. There isn't a class like Zend_Db_Update or Zend_Db_Delete to build the update and delete query's like you build the select. To fix this we extended the Zend_Db_Select class as you can see in the code below. The code shows the custom class that extends the Zend_Db_Select class with some minimal example code at the bottom to show how it's used.
<?php
class Unica_Model_Statement extends Zend_Db_Select
{
public function __construct($oMapper)
{
parent::__construct($oMapper->getAdapter());
$this->from($oMapper->getTableName());
}
/**
* #desc Make a string that can be used for updates and delete
* From the string "SELECT `column` FROM `tabelnaam` WHERE `id` = 1" only the part "`id = `" is returned.
* #return string
*/
public function toAltString()
{
$sQuery = $this->assemble(); // Get the full query string
$sFrom = $this->_renderFrom(''); // Get the FROM part of the string
// Get the text after the FROM (and therefore not using the "SELECT `colname`" part)
$sString = strstr($sQuery,$sFrom);
// Delete the FROM itself from the query (therefore deleting the "FROM `tabelnaam`" part)
$sString = str_replace($sFrom, '', $sString);
// Delete the word "WHERE" from the string.
$sString = str_replace('WHERE', '', $sString);
return $sString;
}
}
################################################
# Below code is just to demonstrate the usage. #
################################################
class Default_IndexController extends Zend_Controller_Action
{
public function indexAction()
{
$person = new Unica_Model_Person_Entity();
$statement = new Unica_Model_Statement($person->getMapper());
$statement->where('id = ?' , 1);
$person->getMapper()->delete($statement);
}
}
class Unica_Model_Person_Mapper
{
public function delete($statement)
{
$where = $statement->toAltString();
$this->getAdapter()->delete($this->_tableName,$where);
}
}
Everything works fine using this class but it got us wondering if we were maybe missing something. Is there a reason there aren't default update/delete classes like there is for select and will using this class give us trouble elsewhere?
Advice would be appreciated.
Thanks in advance,
Ilians

Answer 1

The class is fine if you are sure you are not going to make it evolve too much in the future. I assume your approach is to benefit from the automatic quoting in the Zend_Db_Select class. In my humble opinion, however, it has some design pitfalls that could lead to extensibility troubles if you need to modify or extend it:
It's receiving some data that is discarded afterwards (the entity object, to use the "from" clause).
It's manipulating directly the SQL output of the select query, which can be something dangerous to rely upon. If the format changes, and also if you need to include more elements to the where clause, your code could get quite "muddy" to adapt to the changes.
My approach would just be to use the where clauses directly in the code, and quote them wherever it's necessary. It doesn't look particularly less clean to me. Something like the following:
$db->delete('tablename', 'id = ' . $db->quote('1'));
Eventually, you could even abstract it into a method or class, to avoid having to spread $db->quote() calls all over the place, something like that:
private function myDelete($tableName, $fieldName, $fieldValue)
{
$this->db->delete($tableName, $fieldName . ' = ' . $db->quote($fieldValue));
}
EDIT: Including multiple clauses in the where part would make it a bit more involved, and how flexible you want to be will depend on your particular application. For instance, a possible solution for several "ANDed" clauses could be the following:
private function myDelete($tableName, array $fields)
{
$whereClauses = array();
foreach ($fields as $fieldName => $fieldValue) {
$whereClauses[] = $fieldName . ' = ' . $db->quote($fieldValue);
}
$this->db->delete($tableName, implode(' AND ', $whereClauses));
}
$this->myDelete('tablename', array('id' => '1', 'name' => 'john'));
Hope that helps,

Answer 2

I dont know the exact reasoning behind Zend_Db_Select not offering CUD methods. The obvious explanation is that Select means you should use it for just that: dynamic query building. To insert, update and delete you would either use Zend_Db_Adapter or the proxy methods to it in Zend_Db_Table and Zend_Db_Table_Row or the generic Zend_Db_Statement.
However, with that said, I think there is nothing wrong with extending Zend_Db_Select and adjusting it your needs (just like any other component that doesnt do what you want initially)