You need to dig more into Magento to understand how Magento ORM works (what the EAV structure and how collections actually work).
To get all product attributes, this is true:
$collection = Mage::getModel('catalog/product')->getCollection()->addAttributeToSelect('*');
What you are missing is the fact that Magento will not give you all the related queries for the collection when you do:
echo $collection->getSelect()
When you run the code only to retrieve the collection, Magento will only run the following query:
SELECT `e`.* FROM `catalog_product_entity` AS `e`
When you start a loop through a collection:
$collection = Mage::getModel('catalog/product')->getCollection()->addAttributeToSelect('*'); foreach($collection as $p) { echo $p->getName()."\n";
Magento will run additional queries to get all attributes and values:
SELECT `main_table`.`entity_type_id`, `main_table`.`attribute_code`, `main_table`.`attribute_model`, `main_table`.`backend_model`, `main_table`.`backend_type`, `main_table`.`backend_table`, `main_table`.`frontend_model`, `main_table`.`frontend_input`, `main_table`.`frontend_label`, `main_table`.`frontend_class`, `main_table`.`source_model`, `main_table`.`is_required`, `main_table`.`is_user_defined`, `main_table`.`default_value`, `main_table`.`is_unique`, `main_table`.`note`, `additional_table`.* FROM `eav_attribute` AS `main_table` INNER JOIN `catalog_eav_attribute` AS `additional_table` ON additional_table.attribute_id = main_table.attribute_id WHERE (main_table.entity_type_id = 10) SELECT `t_d`.`entity_id`, `t_d`.`attribute_id`, `t_d`.`value` AS `default_value`, `t_s`.`value` AS `store_value`, IF(t_s.value_id IS NULL, t_d.value, t_s.value) AS `value` FROM `catalog_product_entity_text` AS `t_d` LEFT JOIN `catalog_product_entity_text` AS `t_s` ON t_s.attribute_id = t_d.attribute_id AND t_s.entity_id = t_d.entity_id AND t_s.store_id = 1 WHERE (t_d.entity_type_id = 10) AND (t_d.entity_id IN (16, 17, 18, 19, 20, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 41, 42, 44, 45, 46, 47, 48, 49, 51, 52, 53, 54, 74, 75, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166)) AND (t_d.attribute_id IN ('496', '507', '531', '97', '494', '509', '499', '492', '498', '104', '495', '497', '936', '500', '476', '506')) AND (t_d.store_id = 0) UNION ALL SELECT `t_d`.`entity_id`, `t_d`.`attribute_id`, `t_d`.`value` AS `default_value`, `t_s`.`value` AS `store_value`, IF(t_s.value_id IS NULL, t_d.value, t_s.value) AS `value` FROM `catalog_product_entity_int` AS `t_d` LEFT JOIN `catalog_product_entity_int` AS `t_s` ON t_s.attribute_id = t_d.attribute_id AND t_s.entity_id = t_d.entity_id AND t_s.store_id = 1 WHERE (t_d.entity_type_id = 10) AND (t_d.entity_id IN (16, 17, 18, 19, 20, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 41, 42, 44, 45, 46, 47, 48, 49, 51, 52, 53, 54, 74, 75, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166)) AND (t_d.attribute_id IN ('272', '510', '875', '877', '903', '501', '935', '952', '904', '102', '513', '110', '859', '862', '508', '863', '525', '502', '107', '860', '273', '274', '526', '861')) AND (t_d.store_id = 0) UNION ALL SELECT `t_d`.`entity_id`, `t_d`.`attribute_id`, `t_d`.`value` AS `default_value`, `t_s`.`value` AS `store_value`, IF(t_s.value_id IS NULL, t_d.value, t_s.value) AS `value` FROM `catalog_product_entity_decimal` AS `t_d` LEFT JOIN `catalog_product_entity_decimal` AS `t_s` ON t_s.attribute_id = t_d.attribute_id AND t_s.entity_id = t_d.entity_id AND t_s.store_id = 1 WHERE (t_d.entity_type_id = 10) AND (t_d.entity_id IN (16, 17, 18, 19, 20, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 41, 42, 44, 45, 46, 47, 48, 49, 51, 52, 53, 54, 74, 75, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166)) AND (t_d.attribute_id IN ('100', '960', '503', '943', '99', '567', '270', '101')) AND (t_d.store_id = 0) UNION ALL SELECT `t_d`.`entity_id`, `t_d`.`attribute_id`, `t_d`.`value` AS `default_value`, `t_s`.`value` AS `store_value`, IF(t_s.value_id IS NULL, t_d.value, t_s.value) AS `value` FROM `catalog_product_entity_varchar` AS `t_d` LEFT JOIN `catalog_product_entity_varchar` AS `t_s` ON t_s.attribute_id = t_d.attribute_id AND t_s.entity_id = t_d.entity_id AND t_s.store_id = 1 WHERE (t_d.entity_type_id = 10) AND (t_d.entity_id IN (16, 17, 18, 19, 20, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 41, 42, 44, 45, 46, 47, 48, 49, 51, 52, 53, 54, 74, 75, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166)) AND (t_d.attribute_id IN ('940', '571', '271', '562', '878', '106', '879', '906', '873', '703', '105', '103', '942', '941', '96', '836', '931', '874', '876', '905', '109', '880', '493', '881', '481', '570')) AND (t_d.store_id = 0) UNION ALL SELECT `t_d`.`entity_id`, `t_d`.`attribute_id`, `t_d`.`value` AS `default_value`, `t_s`.`value` AS `store_value`, IF(t_s.value_id IS NULL, t_d.value, t_s.value) AS `value` FROM `catalog_product_entity_datetime` AS `t_d` LEFT JOIN `catalog_product_entity_datetime` AS `t_s` ON t_s.attribute_id = t_d.attribute_id AND t_s.entity_id = t_d.entity_id AND t_s.store_id = 1 WHERE (t_d.entity_type_id = 10) AND (t_d.entity_id IN (16, 17, 18, 19, 20, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 41, 42, 44, 45, 46, 47, 48, 49, 51, 52, 53, 54, 74, 75, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166)) AND (t_d.attribute_id IN ('572', '573', '704', '705', '568', '569')) AND (t_d.store_id = 0)
To learn more about what queries are running in different contexts, create an empty script, load only the Mage::app() and play with the collections and install $ _logAllQueries to true in Varien_Db_Adapter_Pdo_Mysql . Additional information: here .