diff --git a/lib/base.php b/lib/base.php
index 52793fc..c4da57f 100644
--- a/lib/base.php
+++ b/lib/base.php
@@ -39,10 +39,11 @@ abstract class Base extends \OC\User\Backend{
 	 * @return bool
 	 */
 	public function deleteUser($uid) {
-		\OC::$server->getDatabaseConnection()->executeQuery(
-			'DELETE FROM `*PREFIX*users_external` WHERE `uid` = ? AND `backend` = ?',
-			array($uid, $this->backend)
-		);
+		$query = \OC::$server->getDatabaseConnection()->getQueryBuilder();
+		$query->delete('users_external')
+			->where($query->expr()->eq('uid', $query->createNamedParameter($uid)))
+			->andWhere($query->expr()->eq('backend', $query->createNamedParameter($this->backend)));
+		$query->execute();
 		return true;
 	}
 
@@ -54,11 +55,15 @@ abstract class Base extends \OC\User\Backend{
 	 * @return string display name
 	 */
 	public function getDisplayName($uid) {
-		$user = \OC::$server->getDatabaseConnection()->executeQuery(
-			'SELECT `displayname` FROM `*PREFIX*users_external`'
-			. ' WHERE `uid` = ? AND `backend` = ?',
-			array($uid, $this->backend)
-		)->fetch();
+		$query = \OC::$server->getDatabaseConnection()->getQueryBuilder();
+		$query->select('displayname')
+			->from('users_external')
+			->where($query->expr()->eq('uid', $query->createNamedParameter($uid)))
+			->andWhere($query->expr()->eq('backend', $query->createNamedParameter($this->backend)));
+		$result = $query->execute();
+		$user = $result->fetch();
+		$result->closeCursor();
+
 		$displayName = trim($user['displayname'], ' ');
 		if (!empty($displayName)) {
 			return $displayName;
@@ -73,19 +78,27 @@ abstract class Base extends \OC\User\Backend{
 	 * @return array with all displayNames (value) and the corresponding uids (key)
 	 */
 	public function getDisplayNames($search = '', $limit = null, $offset = null) {
-		$stmt = \OC::$server->getDatabaseConnection()->prepare(
-			'SELECT `uid`, `displayname` FROM `*PREFIX*users_external`'
-			. ' WHERE (LOWER(`displayname`) LIKE LOWER(?) '
-			. ' OR LOWER(`uid`) LIKE LOWER(?)) AND `backend` = ?',
-			$limit, $offset
-		);
 
-		$stmt->execute(['%' . $search . '%', '%' . $search . '%', $this->backend]);
+		$connection = \OC::$server->getDatabaseConnection();
+		$query = $connection->getQueryBuilder();
+		$query->select('uid', 'displayname')
+			->from('users_external')
+			->where($query->expr()->iLike('displayname', $query->createNamedParameter('%' . $connection->escapeLikeParameter($search) . '%')))
+			->andWhere($query->expr()->iLike('uid', $query->createNamedParameter('%' . $connection->escapeLikeParameter($search) . '%')))
+			->andWhere($query->expr()->eq('backend', $query->createNamedParameter($this->backend)));
+		if ($limit) {
+			$query->setMaxResults($limit);
+		}
+		if ($offset) {
+			$query->setFirstResult($offset);
+		}
+		$result = $query->execute();
 
-		$displayNames = array();
-		while ($row = $stmt->fetch()) {
+		$displayNames = [];
+		while ($row = $result->fetch()) {
 			$displayNames[$row['uid']] = $row['displayname'];
 		}
+		$result->closeCursor();
 
 		return $displayNames;
 	}
@@ -96,18 +109,26 @@ abstract class Base extends \OC\User\Backend{
 	* @return array with all uids
 	*/
 	public function getUsers($search = '', $limit = null, $offset = null) {
-		$stmt = \OC::$server->getDatabaseConnection()->prepare(
-			'SELECT `uid` FROM `*PREFIX*users_external`'
-				. ' WHERE LOWER(`uid`) LIKE LOWER(?) AND `backend` = ?',
-			$limit, $offset
-		);
+		$connection = \OC::$server->getDatabaseConnection();
+		$query = $connection->getQueryBuilder();
+		$query->select('uid')
+			->from('users_external')
+			->where($query->expr()->iLike('uid', $query->createNamedParameter($connection->escapeLikeParameter($search) . '%')))
+			->andWhere($query->expr()->eq('backend', $query->createNamedParameter($this->backend)));
+		if ($limit) {
+			$query->setMaxResults($limit);
+		}
+		if ($offset) {
+			$query->setFirstResult($offset);
+		}
+		$result = $query->execute();
 
-		$stmt->execute([$search . '%', $this->backend]);
-
-		$users = array();
-		while ($row = $stmt->fetch()) {
+		$users = [];
+		while ($row = $result->fetch()) {
 			$users[] = $row['uid'];
 		}
+		$result->closeCursor();
+
 		return $users;
 	}
 
@@ -132,11 +153,14 @@ abstract class Base extends \OC\User\Backend{
 		if (!$this->userExists($uid)) {
 			return false;
 		}
-		\OC::$server->getDatabaseConnection()->executeQuery(
-			'UPDATE `*PREFIX*users_external` SET `displayname` = ?'
-			. ' WHERE LOWER(`uid`) = ? AND `backend` = ?',
-			array($displayName, $uid, $this->backend)
-		);
+
+		$query = \OC::$server->getDatabaseConnection()->getQueryBuilder();
+		$query->update('users_external')
+			->set('displayname', $query->createNamedParameter($displayName))
+			->where($query->expr()->eq('uid', $query->createNamedParameter($uid)))
+			->andWhere($query->expr()->eq('backend', $query->createNamedParameter($this->backend)));
+		$query->execute();
+
 		return true;
 	}
 
@@ -150,11 +174,14 @@ abstract class Base extends \OC\User\Backend{
 	protected function storeUser($uid)
 	{
 		if (!$this->userExists($uid)) {
-			\OC::$server->getDatabaseConnection()->executeQuery(
-				'INSERT INTO `*PREFIX*users_external` ( `uid`, `backend` )'
-				. ' VALUES( ?, ? )',
-				array($uid, $this->backend)
-			);
+
+			$query = \OC::$server->getDatabaseConnection()->getQueryBuilder();
+			$query->insert('users_external')
+				->values([
+					'uid' => $query->createNamedParameter($uid),
+					'backend' => $query->createNamedParameter($this->backend),
+				]);
+			$query->execute();
 		}
 	}
 
@@ -166,11 +193,16 @@ abstract class Base extends \OC\User\Backend{
 	 * @return boolean
 	 */
 	public function userExists($uid) {
-		$result = \OC::$server->getDatabaseConnection()->executeQuery(
-			'SELECT COUNT(*) FROM `*PREFIX*users_external`'
-			. ' WHERE LOWER(`uid`) = LOWER(?) AND `backend` = ?',
-			array($uid, $this->backend)
-		);
-		return $result->fetch() > 0;
+		$connection = \OC::$server->getDatabaseConnection();
+		$query = $connection->getQueryBuilder();
+		$query->select($query->func()->count('*', 'num_users'))
+			->from('users_external')
+			->where($query->expr()->iLike('uid', $query->createNamedParameter($connection->escapeLikeParameter($uid))))
+			->andWhere($query->expr()->eq('backend', $query->createNamedParameter($this->backend)));
+		$result = $query->execute();
+		$users = $result->fetchColumn();
+		$result->closeCursor();
+
+		return $users > 0;
 	}
 }
diff --git a/lib/imap.php b/lib/imap.php
index cf96cbf..604674d 100644
--- a/lib/imap.php
+++ b/lib/imap.php
@@ -52,25 +52,29 @@ class OC_User_IMAP extends \OCA\user_external\Base {
 			$uid = str_replace("%40","@",$uid);
 		}
 
-                $result = \OC::$server->getDatabaseConnection()->executeQuery(
-                        'SELECT `userid` FROM `*PREFIX*preferences` WHERE `appid`=? AND `configkey`=? AND `configvalue`=?',
-                        array('settings','email',$uid)
-                );
+		$query = \OC::$server->getDatabaseConnection()->getQueryBuilder();
+		$query->select('userid')
+			->from('preferences')
+			->where($query->expr()->eq('appid', $query->createNamedParameter('settings')))
+			->andWhere($query->expr()->eq('configkey', $query->createNamedParameter('email')))
+			->andWhere($query->expr()->eq('configvalue', $query->createNamedParameter($uid)));
+		$result = $query->execute();
 
-		$users = array();
+		$users = [];
 		while ($row = $result->fetch()) {
 			$users[] = $row['userid'];
 		}
+		$result->closeCursor();
 
 		if(count($users) === 1) {
 			$username = $uid;
 			$uid = $users[0];
  		// Check if we only want logins from ONE domain and strip the domain part from UID
-	}elseif($this->domain !== '') {
+		}elseif($this->domain !== '') {
  			$pieces = explode('@', $uid);
  			if(count($pieces) === 1) {
  				$username = $uid . "@" . $this->domain;
- 			}elseif((count($pieces) === 2) and ($pieces[1] === $this->domain)) {
+ 			}elseif((count($pieces) === 2) && ($pieces[1] === $this->domain)) {
  				$username = $uid;
  				$uid = $pieces[0];
  			}else{
@@ -83,13 +87,13 @@ class OC_User_IMAP extends \OCA\user_external\Base {
  		$mbox = @imap_open($this->mailbox, $username, $password, OP_HALFOPEN, 1);
 		imap_errors();
 		imap_alerts();
-		if($mbox !== FALSE) {
+		if($mbox !== false) {
 			imap_close($mbox);
 			$uid = mb_strtolower($uid);
 			$this->storeUser($uid);
 			return $uid;
-		}else{
-			return false;
 		}
+
+		return false;
 	}
 }