Исправление внесено в агрегации.sql, добавлено решение по разделу функции

ebelykh/postgresql/агрегации и группировки/агрегации.sql

@@ -13,7 +13,7 @@ SELECT customer_id,
 FROM visits v
 LEFT JOIN transactions t
 ON v.visit_id = t.visit_id
-WHERE transaction_id IS NULL
+WHERE t.transaction_id IS NULL
 GROUP BY customer_id;
 
 --Задача 1141 

ebelykh/postgresql/функции/функции.sql

@@ -0,0 +1,20 @@
+--Задача 1211
+SELECT
+    query_name,
+    ROUND(AVG(rating * 1.0 / position), 2) AS quality,
+    ROUND(AVG(CASE WHEN rating < 3 THEN 1 ELSE 0 END) * 100,2) AS poor_query_percentage
+FROM Queries
+GROUP BY query_name;
+
+--Задача 1193
+SELECT
+    TO_CHAR(trans_date, 'YYYY-MM') AS month,
+    country,
+    COUNT(*) AS trans_count,
+    SUM(CASE WHEN state = 'approved' THEN 1 ELSE 0 END) AS approved_count,
+    SUM(amount) AS trans_total_amount,
+    SUM(CASE WHEN state = 'approved' THEN amount ELSE 0 END) AS approved_total_amount
+FROM Transactions
+GROUP BY
+    TO_CHAR(trans_date, 'YYYY-MM'),
+    country;