diff --git a/php/model/DatabaseCommentManager.php b/php/model/DatabaseCommentManager.php
index 3bba78c..df4124c 100644
--- a/php/model/DatabaseCommentManager.php
+++ b/php/model/DatabaseCommentManager.php
@@ -162,11 +162,22 @@ class DatabaseCommentManager implements CommentManagerDAO
             $db = $this->getConnection();
 
             $sql = "
-                SELECT *
-                FROM comments
-                WHERE article_id = :articleId
-                ORDER BY created ASC
-            ";
+            SELECT
+                id,
+                article_id,
+                CASE
+                    WHEN parent_comment_id IS NULL THEN NULL
+                    WHEN parent_comment_id = '' THEN NULL
+                    WHEN parent_comment_id = 0 THEN NULL
+                    ELSE parent_comment_id
+                END AS parent_comment_id,
+                author,
+                content,
+                created
+            FROM comments
+            WHERE article_id = :articleId
+            ORDER BY created ASC
+        ";
 
             $command = $db->prepare($sql);