diff --git a/includes/model/ShiftEntry_model.php b/includes/model/ShiftEntry_model.php
index e3046152..0cf5c040 100644
--- a/includes/model/ShiftEntry_model.php
+++ b/includes/model/ShiftEntry_model.php
@@ -7,9 +7,12 @@ function ShiftEntries_freeleaded_count() {
   return sql_select_single_cell("SELECT COUNT(*) FROM `ShiftEntry` WHERE `freeloaded` = 1");
 }
 
+/**
+ * List users subsribed to a given shift.
+ */
 function ShiftEntries_by_shift($shift_id) {
   return sql_select("
-      SELECT `User`.`email`, `User`.`email_shiftinfo`, `User`.`Nick`, `User`.`Sprache`, `ShiftEntry`.`UID`, `ShiftEntry`.`TID`, `ShiftEntry`.`SID`, `AngelTypes`.`name` as `angel_type_name`, `ShiftEntry`.`Comment`, `ShiftEntry`.`freeloaded`
+      SELECT `User`.`Nick`, `User`.`email`, `User`.`email_shiftinfo`, `User`.`Sprache`, `ShiftEntry`.`UID`, `ShiftEntry`.`TID`, `ShiftEntry`.`SID`, `AngelTypes`.`name` as `angel_type_name`, `ShiftEntry`.`Comment`, `ShiftEntry`.`freeloaded`
       FROM `ShiftEntry`
       JOIN `User` ON `ShiftEntry`.`UID`=`User`.`UID`
       JOIN `AngelTypes` ON `ShiftEntry`.`TID`=`AngelTypes`.`id`
@@ -31,6 +34,24 @@ function ShiftEntry_create($shift_entry) {
       `freeloaded`=" . sql_escape($shift_entry['freeloaded'] ? 'TRUE' : 'FALSE'));
 }
 
+/**
+ * Update a shift entry.
+ */
+function ShiftEntry_update($shift_entry) {
+  return sql_query("UPDATE `ShiftEntry` SET
+      `Comment`='" . sql_escape($shift_entry['Comment']) . "',
+      `freeload_comment`='" . sql_escape($shift_entry['freeload_comment']) . "',
+      `freeloaded`=" . sql_escape($shift_entry['freeloaded'] ? 'TRUE' : 'FALSE') . "
+      WHERE `id`=" . sql_escape($shift_entry['id']));
+}
+
+/**
+ * Delete a shift entry.
+ */
+function ShiftEntry_delete($shift_entry_id) {
+  return sql_query("DELETE FROM `ShiftEntry` WHERE `id`=" . sql_escape($shift_entry_id));
+}
+
 /**
  * Returns next (or current) shifts of given user.
  *
diff --git a/includes/model/Shifts_model.php b/includes/model/Shifts_model.php
index 5d0ec4a2..28f84c26 100644
--- a/includes/model/Shifts_model.php
+++ b/includes/model/Shifts_model.php
@@ -1,4 +1,67 @@
 <?php
+
+/**
+ * Delete a shift by its external id.
+ */
+function Shift_delete_by_psid($shift_psid) {
+  return sql_query("DELETE FROM `Shifts` WHERE `PSID`=" . sql_escape($shift_psid));
+}
+
+/**
+ * Delete a shift.
+ */
+function Shift_delete($shift_id) {
+  return sql_query("DELETE FROM `Shifts` WHERE `SID`=" . sql_escape($shift_id));
+}
+
+/**
+ * Update a shift.
+ */
+function Shift_update($shift) {
+  return sql_query("UPDATE `Shifts` SET
+      `start`=" . sql_escape($shift['start']) . ",
+      `end`=" . sql_escape($shift['end']) . ",
+      `RID`=" . sql_escape($shift['RID']) . ",
+      `name`=" . sql_null($shift['name']) . ",
+      `URL`=" . sql_null($shift['URL']) . ",
+      `PSID`=" . sql_null($shift['PSID']) . "
+      WHERE `SID`=" . sql_escape($shift['SID']));
+}
+
+/**
+ * Update a shift by its external id.
+ */
+function Shift_update_by_psid($shift) {
+  return sql_query("UPDATE `Shifts` SET
+      `start`=" . sql_escape($shift['start']) . ",
+      `end`=" . sql_escape($shift['end']) . ",
+      `RID`=" . sql_escape($shift['RID']) . ",
+      `name`=" . sql_null($shift['name']) . ",
+      `URL`=" . sql_null($shift['URL']) . "
+      WHERE `PSID`=" . sql_escape($shift['PSID']));
+}
+
+/**
+ * Create a new shift.
+ *
+ * @return new shift id or false
+ */
+function Shift_create($shift) {
+  $result = sql_query("INSERT INTO `Shifts` SET
+      `start`=" . sql_escape($shift['start']) . ",
+      `end`=" . sql_escape($shift['end']) . ",
+      `RID`=" . sql_escape($shift['RID']) . ",
+      `name`=" . sql_null($shift['name']) . ",
+      `URL`=" . sql_null($shift['URL']) . ",
+      `PSID`=" . sql_null($shift['PSID']));
+  if ($result === false)
+    return false;
+  return sql_id();
+}
+
+/**
+ * Return users shifts.
+ */
 function Shifts_by_user($user) {
   return sql_select("
       SELECT * 
diff --git a/includes/mysqli_provider.php b/includes/mysqli_provider.php
index 9f901a40..9f4f1396 100644
--- a/includes/mysqli_provider.php
+++ b/includes/mysqli_provider.php
@@ -5,16 +5,23 @@
  */
 function sql_close() {
   global $sql_connection;
-
+  
   return $sql_connection->close();
 }
 
+/**
+ * Return NULL if given value is null.
+ */
+function sql_null($value = null) {
+  return $value == null ? 'NULL' : ("'" . sql_escape($value) . "'");
+}
+
 /**
  * Start new transaction.
  */
 function sql_transaction_start() {
   global $sql_nested_transaction_level;
-
+  
   if ($sql_nested_transaction_level ++ == 0)
     return sql_query("BEGIN");
   else
@@ -26,7 +33,7 @@ function sql_transaction_start() {
  */
 function sql_transaction_commit() {
   global $sql_nested_transaction_level;
-
+  
   if (-- $sql_nested_transaction_level == 0)
     return sql_query("COMMIT");
   else
@@ -38,7 +45,7 @@ function sql_transaction_commit() {
  */
 function sql_transaction_rollback() {
   global $sql_nested_transaction_level;
-
+  
   if (-- $sql_nested_transaction_level == 0)
     return sql_query("ROLLBACK");
   else
@@ -48,17 +55,17 @@ function sql_transaction_rollback() {
 /**
  * Logs an sql error.
  *
- * @param string $message
+ * @param string $message          
  * @return false
  */
 function sql_error($message) {
   sql_close();
-
+  
   $message = trim($message) . "\n";
   $message .= debug_string_backtrace() . "\n";
-
+  
   error_log('mysql_provider error: ' . $message);
-
+  
   return false;
 }
 
@@ -77,19 +84,19 @@ function sql_error($message) {
  */
 function sql_connect($host, $user, $pass, $db) {
   global $sql_connection;
-
+  
   $sql_connection = new mysqli($host, $user, $pass, $db);
   if ($sql_connection->connect_errno)
     return sql_error("Unable to connect to MySQL: " . $sql_connection->connect_error);
-
+  
   $result = $sql_connection->query("SET CHARACTER SET utf8;");
   if (! $result)
     return sql_error("Unable to set utf8 character set (" . $sql_connection->errno . ") " . $sql_connection->error);
-
+  
   $result = $sql_connection->set_charset('utf8');
   if (! $result)
     return sql_error("Unable to set utf8 names (" . $sql_connection->errno . ") " . $sql_connection->error);
-
+  
   return $sql_connection;
 }
 
@@ -110,12 +117,12 @@ function sql_select_db($db_name) {
 /**
  * MySQL SELECT query
  *
- * @param string $query
+ * @param string $query          
  * @return Result array or false on error
  */
 function sql_select($query) {
   global $sql_connection;
-
+  
   $result = $sql_connection->query($query);
   if ($result) {
     $data = array();
@@ -129,12 +136,12 @@ function sql_select($query) {
 /**
  * MySQL execute a query
  *
- * @param string $query
+ * @param string $query          
  * @return mysqli_result boolean resource or false on error
  */
 function sql_query($query) {
   global $sql_connection;
-
+  
   $result = $sql_connection->query($query);
   if ($result) {
     return $result;
@@ -155,7 +162,7 @@ function sql_id() {
 /**
  * Escape a string for a sql query.
  *
- * @param string $query
+ * @param string $query          
  * @return string
  */
 function sql_escape($query) {
@@ -166,7 +173,7 @@ function sql_escape($query) {
 /**
  * Count query result lines.
  *
- * @param string $query
+ * @param string $query          
  * @return int Count of result lines
  */
 function sql_num_query($query) {
diff --git a/includes/pages/admin_import.php b/includes/pages/admin_import.php
index 8362391d..120ab91b 100644
--- a/includes/pages/admin_import.php
+++ b/includes/pages/admin_import.php
@@ -1,4 +1,5 @@
 <?php
+
 function admin_import_title() {
   return _("Frab import");
 }
@@ -116,14 +117,23 @@ function admin_import() {
         sql_query("DELETE FROM `Room` WHERE `Name`='" . sql_escape($room) . "' LIMIT 1");
       
       list($events_new, $events_updated, $events_deleted) = prepare_events($import_file);
-      foreach ($events_new as $event)
-        sql_query("INSERT INTO `Shifts` SET `name`='" . sql_escape($event['name']) . "', `start`=" . sql_escape($event['start']) . ", `end`=" . sql_escape($event['end']) . ", `RID`=" . sql_escape($event['RID']) . ", `PSID`=" . sql_escape($event['PSID']) . ", `URL`='" . sql_escape($event['URL']) . "'");
+      foreach ($events_new as $event) {
+        $result = Shift_create($event);
+        if ($result === false)
+          engelsystem_error('Unable to create shift.');
+      }
       
-      foreach ($events_updated as $event)
-        sql_query("UPDATE `Shifts` SET `name`='" . sql_escape($event['name']) . "', `start`=" . sql_escape($event['start']) . ", `end`=" . sql_escape($event['end']) . ", `RID`=" . sql_escape($event['RID']) . ", `PSID`=" . sql_escape($event['PSID']) . ", `URL`='" . sql_escape($event['URL']) . "' WHERE `PSID`=" . sql_escape($event['PSID']) . " LIMIT 1");
+      foreach ($events_updated as $event) {
+        $result = Shift_update_by_psid($event);
+        if ($result === false)
+          engelsystem_error('Unable to update shift.');
+      }
       
-      foreach ($events_deleted as $event)
-        sql_query("DELETE FROM `Shifts` WHERE `PSID`=" . sql_escape($event['PSID']) . " LIMIT 1");
+      foreach ($events_deleted as $event) {
+        $result = Shift_delete_by_psid($event['PSID']);
+        if ($result === false)
+          engelsystem_error('Unable to delete shift.');
+      }
       
       engelsystem_log("Pentabarf import done");
       
@@ -165,7 +175,7 @@ function prepare_rooms($file) {
   
   return array(
       $rooms_new,
-      $rooms_deleted
+      $rooms_deleted 
   );
 }
 
diff --git a/includes/pages/admin_shifts.php b/includes/pages/admin_shifts.php
index 473022eb..fd5b9b55 100644
--- a/includes/pages/admin_shifts.php
+++ b/includes/pages/admin_shifts.php
@@ -1,4 +1,5 @@
 <?php
+
 function admin_shifts_title() {
   return _("Create shifts");
 }
@@ -229,14 +230,17 @@ function admin_shifts() {
           )) 
       ));
     }
-  
   } elseif (isset($_REQUEST['submit'])) {
     if (! is_array($_SESSION['admin_shifts_shifts']) || ! is_array($_SESSION['admin_shifts_types']))
       redirect(page_link_to('admin_shifts'));
     
     foreach ($_SESSION['admin_shifts_shifts'] as $shift) {
-      sql_query("INSERT INTO `Shifts` SET `start`=" . sql_escape($shift['start']) . ",  `end`=" . sql_escape($shift['end']) . ", `RID`=" . sql_escape($shift['RID']) . ", `name`='" . sql_escape($shift['name']) . "'");
-      $shift_id = sql_id();
+      $shift['URL'] = null;
+      $shift['PSID'] = null;
+      $shift_id = Shift_create($shift);
+      if ($shift_id === false)
+        engelsystem_error('Unable to create shift.');
+      
       engelsystem_log("Shift created: " . $shift['name'] . " from " . date("Y-m-d H:i", $shift['start']) . " to " . date("Y-m-d H:i", $shift['end']));
       $needed_angel_types_info = array();
       foreach ($_SESSION['admin_shifts_types'] as $type_id => $count) {
diff --git a/includes/pages/admin_user.php b/includes/pages/admin_user.php
index 87190857..4e10ca1e 100644
--- a/includes/pages/admin_user.php
+++ b/includes/pages/admin_user.php
@@ -215,7 +215,6 @@ function admin_user() {
             $user_source = sql_select("SELECT `Nick`, `UID` FROM `User` WHERE `UID` = '" . sql_escape($id) . "' LIMIT 1");
             sql_query("DELETE FROM `User` WHERE `UID`=" . sql_escape($id) . " LIMIT 1");
             sql_query("DELETE FROM `UserGroups` WHERE `uid`=" . sql_escape($id));
-            sql_query("UPDATE `ShiftEntry` SET `UID`=0, `Comment`=NULL WHERE `UID`=" . sql_escape($id));
             engelsystem_log("Deleted user " . User_Nick_render($user_source));
             $html .= success("Benutzer gelöscht!", true);
           } else {
diff --git a/includes/pages/user_myshifts.php b/includes/pages/user_myshifts.php
index d1c60dd6..d74475d2 100644
--- a/includes/pages/user_myshifts.php
+++ b/includes/pages/user_myshifts.php
@@ -57,12 +57,15 @@ function user_myshifts() {
         
         $comment = strip_request_item_nl('comment');
         $user_source = User($shift['UID']);
-        sql_query("UPDATE `ShiftEntry` SET 
-            `Comment`='" . sql_escape($comment) . "',
-            `freeloaded`=" . sql_escape($freeloaded ? 1 : 0) . ",
-            `freeload_comment`='" . sql_escape($freeload_comment) . "'
-            WHERE `id`=" . sql_escape($id) . " 
-            LIMIT 1");
+        $result = ShiftEntry_update(array(
+            'id' => $id,
+            'Comment' => $comment,
+            'freeloaded' => $freeloaded,
+            'freeload_comment' => $freeload_comment 
+        ));
+        if ($result === false)
+          engelsystem_error('Unable to update shift entr.');
+        
         engelsystem_log("Updated " . User_Nick_render($user_source) . "'s shift " . $shift['name'] . " from " . date("y-m-d H:i", $shift['start']) . " to " . date("y-m-d H:i", $shift['end']) . " with comment " . $comment);
         success(_("Shift saved."));
         redirect(page_link_to('users') . '&action=view&user_id=' . $shifts_user['UID']);
@@ -77,15 +80,16 @@ function user_myshifts() {
     if (count($shift) > 0) {
       $shift = $shift[0];
       if (($shift['start'] > time() + $LETZTES_AUSTRAGEN * 3600) || in_array('user_shifts_admin', $privileges)) {
-        sql_query("DELETE FROM `ShiftEntry` WHERE `id`=" . sql_escape($id) . " LIMIT 1");
-        $msg .= success(_("You have been signed off from the shift."), true);
+        $result = ShiftEntry_delete($id);
+        if ($result === false)
+          engelsystem_error('Unable to delete shift entry.');
+        success(_("You have been signed off from the shift."));
       } else
-        $msg .= error(_("It's too late to sign yourself off the shift. If neccessary, ask the dispatcher to do so."), true);
+        error(_("It's too late to sign yourself off the shift. If neccessary, ask the dispatcher to do so."));
     } else
       redirect(page_link_to('user_myshifts'));
   }
   
-  msg();
   redirect(page_link_to('users') . '&action=view');
 }
 ?>
diff --git a/includes/pages/user_shifts.php b/includes/pages/user_shifts.php
index ee8e3b19..c1a5cc91 100644
--- a/includes/pages/user_shifts.php
+++ b/includes/pages/user_shifts.php
@@ -20,7 +20,10 @@ function user_shifts() {
     $shift_entry_source = sql_select("SELECT `User`.`Nick`, `ShiftEntry`.`Comment`, `ShiftEntry`.`UID`, `Shifts`.*, `Room`.`Name`, `AngelTypes`.`name` as `angel_type` FROM `ShiftEntry` JOIN `User` ON (`User`.`UID`=`ShiftEntry`.`UID`) JOIN `AngelTypes` ON (`ShiftEntry`.`TID` = `AngelTypes`.`id`) JOIN `Shifts` ON (`ShiftEntry`.`SID` = `Shifts`.`SID`) JOIN `Room` ON (`Shifts`.`RID` = `Room`.`RID`) WHERE `ShiftEntry`.`id`=" . sql_escape($entry_id) . " LIMIT 1");
     if (count($shift_entry_source) > 0) {
       $shift_entry_source = $shift_entry_source[0];
-      sql_query("DELETE FROM `ShiftEntry` WHERE `id`=" . sql_escape($entry_id) . " LIMIT 1");
+      
+      $result = ShiftEntry_delete($entry_id);
+      if ($result === false)
+        engelsystem_error('Unable to delete shift entry.');
       
       engelsystem_log("Deleted " . User_Nick_render($shift_entry_source) . "'s shift: " . $shift_entry_source['name'] . " at " . $shift_entry_source['Name'] . " from " . date("y-m-d H:i", $shift_entry_source['start']) . " to " . date("y-m-d H:i", $shift_entry_source['end']) . " as " . $shift_entry_source['angel_type']);
       success(_("Shift entry deleted."));
@@ -122,7 +125,13 @@ function user_shifts() {
       }
       
       if ($ok) {
-        sql_query("UPDATE `Shifts` SET `start`=" . sql_escape($start) . ", `end`=" . sql_escape($end) . ", `RID`=" . sql_escape($rid) . ", `name`='" . sql_escape($name) . "' WHERE `SID`=" . sql_escape($shift_id) . " LIMIT 1");
+        $shift['name'] = $name;
+        $shift['RID'] = $rid;
+        $shift['start'] = $start;
+        $shift['end'] = $end;
+        $result = Shift_update($shift);
+        if ($result === false)
+          engelsystem_error('Unable to update shift.');
         sql_query("DELETE FROM `NeededAngelTypes` WHERE `shift_id`=" . sql_escape($shift_id));
         $needed_angel_types_info = array();
         foreach ($needed_angel_types as $type_id => $count) {
@@ -169,9 +178,9 @@ function user_shifts() {
     
     // Schicht löschen bestätigt
     if (isset($_REQUEST['delete'])) {
-      sql_query("DELETE FROM `ShiftEntry` WHERE `SID`=" . sql_escape($shift_id));
-      sql_query("DELETE FROM `NeededAngelTypes` WHERE `shift_id`=" . sql_escape($shift_id));
-      sql_query("DELETE FROM `Shifts` WHERE `SID`=" . sql_escape($shift_id) . " LIMIT 1");
+      $result = Shift_delete($shift_id);
+      if ($result === false)
+        engelsystem_error('Unable to delete shift.');
       
       engelsystem_log("Deleted shift " . $shift['name'] . " from " . date("y-m-d H:i", $shift['start']) . " to " . date("y-m-d H:i", $shift['end']));
       success(_("Shift deleted."));
diff --git a/public/index.php b/public/index.php
index 0ba203b0..cd77f9f3 100644
--- a/public/index.php
+++ b/public/index.php
@@ -82,7 +82,7 @@ $free_pages = array(
     'api',
     'credits',
     'angeltypes',
-    'users'
+    'users' 
 );
 
 // Gewünschte Seite/Funktion
@@ -91,10 +91,10 @@ if (! isset($_REQUEST['p']))
   $_REQUEST['p'] = isset($user) ? "news" : "login";
 if (isset($_REQUEST['p']) && preg_match("/^[a-z0-9_]*$/i", $_REQUEST['p']) && (in_array($_REQUEST['p'], $free_pages) || in_array($_REQUEST['p'], $privileges))) {
   $p = $_REQUEST['p'];
-
+  
   $title = $p;
   $content = "";
-
+  
   if ($p == "api") {
     require_once realpath(__DIR__ . '/../includes/controller/api.php');
     error("Api disabled temporily.");
@@ -222,7 +222,7 @@ echo template_render('../templates/layout.html', array(
     'content' => msg() . $content,
     'header_toolbar' => header_toolbar(),
     'faq_url' => $faq_url,
-    'locale' => $_SESSION['locale']
+    'locale' => $_SESSION['locale'] 
 ));
 
 counter();