Implement cleaning to set all historic negative balances to zero

postgres/queries/budgets.sql

@@ -11,4 +11,19 @@ WHERE user_budgets.user_id = $1;
 
 -- name: GetBudget :one
 SELECT * FROM budgets 
-WHERE id = $1;
+WHERE id = $1;
+
+-- name: GetFirstActivity :one
+SELECT MIN(dates.min_date)::date as min_date
+FROM (
+        SELECT MIN(assignments.date) as min_date
+        FROM assignments
+        INNER JOIN categories ON categories.id = assignments.category_id
+        INNER JOIN category_groups ON category_groups.id = categories.category_group_id
+        WHERE category_groups.budget_id = @budget_id
+        UNION
+        SELECT MIN(transactions.date) as min_date
+        FROM transactions
+        INNER JOIN accounts ON accounts.id = transactions.account_id
+        WHERE accounts.budget_id = @budget_id
+) dates;