Use date_trunc instead of splitting date into year and month

postgres/schema/202112081529_views-for-months.sql

@@ -1,16 +1,16 @@
 -- +goose Up
 CREATE VIEW transactions_by_month AS 
-        SELECT extract(year from transactions.date) as year, extract(month from transactions.date) as month, transactions.category_id, accounts.budget_id, SUM(amount) as amount
+        SELECT date_trunc('month', transactions.date)::date as date, transactions.category_id, accounts.budget_id, SUM(amount) as amount
         FROM transactions
         INNER JOIN accounts ON accounts.id = transactions.account_id
-        GROUP BY extract(year from transactions.date), extract(month from transactions.date), transactions.category_id, accounts.budget_id;
+        GROUP BY date_trunc('month', transactions.date), transactions.category_id, accounts.budget_id;
 
 CREATE VIEW assignments_by_month AS 
-        SELECT extract(year from assignments.date) as year, extract(month from assignments.date) as month, assignments.category_id, category_groups.budget_id, SUM(amount) as amount
+        SELECT date_trunc('month', assignments.date)::date as date, assignments.category_id, category_groups.budget_id, SUM(amount) as amount
         FROM assignments
         INNER JOIN categories ON categories.id = assignments.category_id
         INNER JOIN category_groups ON categories.category_group_id = category_groups.id
-        GROUP BY extract(year from assignments.date), extract(month from assignments.date), assignments.category_id, category_groups.budget_id;
+        GROUP BY date_trunc('month', assignments.date), assignments.category_id, category_groups.budget_id;
 
 -- +goose Down
 DROP VIEW transactions_by_month;