// norm + perf

git-svn-id: http://dev.prestashop.com/svn/v1/branches/1.5.x@8695 b9a71923-0436-4b27-9f14-aed3839534dd

classes/tax/Tax.php

@@ -137,7 +137,8 @@ class TaxCore extends ObjectModel
 	public function isUsed()
 	{
 		return Db::getInstance()->getValue('
-		SELECT COUNT(*) FROM `'._DB_PREFIX_.'order_detail_tax`
+		SELECT `id_tax`
+		FROM `'._DB_PREFIX_.'order_detail_tax`
 		WHERE `id_tax` = '.(int)$this->id
 		);
 	}