vberetar/postgresql/sql_dates_strings_logic.sql

@@ -13,7 +13,7 @@ ORDER BY days_since_registration DESC;
 -- 2 Задача
 SELECT name,
     LOWER(email) AS email_clean,
-    SUBSTRING(email FROM POSITION('@' IN email) + 1) AS domain
+    SUBSTRING(LOWER(email) FROM POSITION('@' IN LOWER(email)) + 1) AS domain
 FROM users
 WHERE email IS NOT NULL
 ORDER BY domain, name;
@@ -30,6 +30,7 @@ SELECT name,
         WHEN age < 25 THEN 'young'
         WHEN age BETWEEN 25 AND 35 THEN 'adult'
         WHEN age > 35 THEN 'senior'
+        ELSE 'unknown'
     END AS age_group
 FROM users
 ORDER BY age;
@@ -70,17 +71,17 @@ FROM users;
 SELECT name,
     CURRENT_DATE - created_at::date AS days_since_registration,
     CASE
-        WHEN created_at >= CURRENT_DATE - INTERVAL '30 days' THEN 'new'
-        WHEN created_at < CURRENT_DATE - INTERVAL '30 days' 
-            AND created_at > CURRENT_DATE - INTERVAL '180 days' THEN 'middle'
-        WHEN created_at < CURRENT_DATE - INTERVAL '180 days' THEN 'old' 
+        WHEN created_at::date >= CURRENT_DATE - INTERVAL '30 days' THEN 'new'
+        WHEN created_at::date < CURRENT_DATE - INTERVAL '30 days' 
+            AND created_at::date > CURRENT_DATE - INTERVAL '180 days' THEN 'middle'
+        ELSE 'old'
     END AS tenure_group,
     is_active
 FROM users
-ORDER BY created_at >= CURRENT_DATE - INTERVAL '30 days',
-    created_at < CURRENT_DATE - INTERVAL '30 days' 
-        AND created_at > CURRENT_DATE - INTERVAL '180 days',
-    created_at < CURRENT_DATE - INTERVAL '180 days',
+ORDER BY created_at::date >= CURRENT_DATE - INTERVAL '30 days',
+    created_at::date < CURRENT_DATE - INTERVAL '30 days' 
+        AND created_at::date > CURRENT_DATE - INTERVAL '180 days',
+    created_at::date < CURRENT_DATE - INTERVAL '180 days',
     days_since_registration;
 -- Ответ на вопросы
 -- 1. В сегментации по возрасту показывает возраст пользователя,