diff --git a/system/core/CodeIgniter.php b/system/core/CodeIgniter.php
index 8159b19..f3592ea 100644
--- a/system/core/CodeIgniter.php
+++ b/system/core/CodeIgniter.php
@@ -50,7 +50,7 @@
  *  Load the global functions
  * ------------------------------------------------------
  */
-	require(BASEPATH.'core/Common.php');
+	require_once(BASEPATH.'core/Common.php');
 
 /*
  * ------------------------------------------------------
diff --git a/system/core/Common.php b/system/core/Common.php
index 981af45..341402c 100644
--- a/system/core/Common.php
+++ b/system/core/Common.php
@@ -150,7 +150,7 @@
 
 				if (class_exists($name) === FALSE)
 				{
-					require($path.$directory.'/'.$class.'.php');
+					require_once($path.$directory.'/'.$class.'.php');
 				}
 
 				break;
@@ -164,7 +164,7 @@
 
 			if (class_exists($name) === FALSE)
 			{
-				require(APPPATH.$directory.'/'.config_item('subclass_prefix').$class.'.php');
+				require_once(APPPATH.$directory.'/'.config_item('subclass_prefix').$class.'.php');
 			}
 		}
 
diff --git a/system/database/drivers/mssql/mssql_driver.php b/system/database/drivers/mssql/mssql_driver.php
index a62ea94..a5ace02 100644
--- a/system/database/drivers/mssql/mssql_driver.php
+++ b/system/database/drivers/mssql/mssql_driver.php
@@ -465,7 +465,7 @@
 			$orderby = 'ORDER BY '.implode(', ', $this->qb_orderby);
 
 			// We have to strip the ORDER BY clause
-			$sql = trim(substr($sql, 0, strrpos($sql, 'ORDER BY '.$orderby)));
+			$sql = trim(substr($sql, 0, strrpos($sql, $orderby)));
 
 			return 'SELECT '.(count($this->qb_select) === 0 ? '*' : implode(', ', $this->qb_select))." FROM (\n"
 				.preg_replace('/^(SELECT( DISTINCT)?)/i', '\\1 ROW_NUMBER() OVER('.$orderby.') AS '.$this->escape_identifiers('CI_rownum').', ', $sql)
diff --git a/system/database/drivers/pdo/subdrivers/pdo_dblib_driver.php b/system/database/drivers/pdo/subdrivers/pdo_dblib_driver.php
index 2346e68..7c4b008 100644
--- a/system/database/drivers/pdo/subdrivers/pdo_dblib_driver.php
+++ b/system/database/drivers/pdo/subdrivers/pdo_dblib_driver.php
@@ -232,7 +232,7 @@
 			$orderby = 'ORDER BY '.implode(', ', $this->qb_orderby);
 
 			// We have to strip the ORDER BY clause
-			$sql = trim(substr($sql, 0, strrpos($sql, 'ORDER BY '.$orderby)));
+			$sql = trim(substr($sql, 0, strrpos($sql, $orderby)));
 
 			return 'SELECT '.(count($this->qb_select) === 0 ? '*' : implode(', ', $this->qb_select))." FROM (\n"
 				.preg_replace('/^(SELECT( DISTINCT)?)/i', '\\1 ROW_NUMBER() OVER('.$orderby.') AS '.$this->escape_identifiers('CI_rownum').', ', $sql)
diff --git a/system/database/drivers/pdo/subdrivers/pdo_sqlsrv_driver.php b/system/database/drivers/pdo/subdrivers/pdo_sqlsrv_driver.php
index ee7c1d1..fd1c4b2 100644
--- a/system/database/drivers/pdo/subdrivers/pdo_sqlsrv_driver.php
+++ b/system/database/drivers/pdo/subdrivers/pdo_sqlsrv_driver.php
@@ -266,7 +266,7 @@
 			$orderby = 'ORDER BY '.implode(', ', $this->qb_orderby);
 
 			// We have to strip the ORDER BY clause
-			$sql = trim(substr($sql, 0, strrpos($sql, 'ORDER BY '.$orderby)));
+			$sql = trim(substr($sql, 0, strrpos($sql, $orderby)));
 
 			return 'SELECT '.(count($this->qb_select) === 0 ? '*' : implode(', ', $this->qb_select))." FROM (\n"
 				.preg_replace('/^(SELECT( DISTINCT)?)/i', '\\1 ROW_NUMBER() OVER('.$orderby.') AS '.$this->escape_identifiers('CI_rownum').', ', $sql)
diff --git a/system/database/drivers/sqlsrv/sqlsrv_driver.php b/system/database/drivers/sqlsrv/sqlsrv_driver.php
index a6739d1..3ffbd4c 100644
--- a/system/database/drivers/sqlsrv/sqlsrv_driver.php
+++ b/system/database/drivers/sqlsrv/sqlsrv_driver.php
@@ -460,7 +460,7 @@
 			$orderby = 'ORDER BY '.implode(', ', $this->qb_orderby);
 
 			// We have to strip the ORDER BY clause
-			$sql = trim(substr($sql, 0, strrpos($sql, 'ORDER BY '.$orderby)));
+			$sql = trim(substr($sql, 0, strrpos($sql, $orderby)));
 
 			return 'SELECT '.(count($this->qb_select) === 0 ? '*' : implode(', ', $this->qb_select))." FROM (\n"
 				.preg_replace('/^(SELECT( DISTINCT)?)/i', '\\1 ROW_NUMBER() OVER('.$orderby.') AS '.$this->escape_identifiers('CI_rownum').', ', $sql)