diff --git a/learntools/sql/ex6.py b/learntools/sql/ex6.py
index ffd11814f..a5aa220b9 100644
--- a/learntools/sql/ex6.py
+++ b/learntools/sql/ex6.py
@@ -36,7 +36,7 @@
                          SELECT a.owner_user_id AS user_id, COUNT(1) AS number_of_answers
                          FROM `bigquery-public-data.stackoverflow.posts_questions` AS q
                          INNER JOIN `bigquery-public-data.stackoverflow.posts_answers` AS a
-                             ON q.id = a.parent_Id
+                             ON q.id = a.parent_id
                          WHERE q.tags LIKE '%bigquery%'
                          GROUP BY a.owner_user_id
                          """
@@ -166,7 +166,7 @@ class BigQueryExperts(CodingProblem):
                          SELECT a.owner_user_id AS user_id, COUNT(1) AS number_of_answers
                          FROM `bigquery-public-data.stackoverflow.posts_questions` AS q
                          INNER JOIN `bigquery-public-data.stackoverflow.posts_answers` AS a
-                             ON q.id = a.parent_Id
+                             ON q.id = a.parent_id
                          WHERE q.tags LIKE '%bigquery%'
                          GROUP BY a.owner_user_id
                          \"""
@@ -219,7 +219,7 @@ def expert_finder(topic, client):
                SELECT a.owner_user_id AS user_id, COUNT(1) AS number_of_answers
                FROM `bigquery-public-data.stackoverflow.posts_questions` AS q
                INNER JOIN `bigquery-public-data.stackoverflow.posts_answers` AS a
-                   ON q.id = a.parent_Id
+                   ON q.id = a.parent_id
                WHERE q.tags like '%{topic}%'
                GROUP BY a.owner_user_id
                \"""