From aceb8a6c06fbd299cc535e5b6fe937fcdadb8fcc Mon Sep 17 00:00:00 2001
From: Yue Zhou <yuezhou@Yues-Air.home>
Date: Sat, 16 Aug 2025 11:34:50 +0200
Subject: [PATCH] solved lab

---
 aggregation&transformation.sql | 76 ++++++++++++++++++++++++++++++++++
 1 file changed, 76 insertions(+)
 create mode 100644 aggregation&transformation.sql

diff --git a/aggregation&transformation.sql b/aggregation&transformation.sql
new file mode 100644
index 0000000..6140fa7
--- /dev/null
+++ b/aggregation&transformation.sql
@@ -0,0 +1,76 @@
+# Determine the **shortest and longest movie durations** and name the values as `max_duration` and `min_duration`.
+select max(length) as max_duration,
+	   min(length) as min_duration
+from sakila.film;
+
+# Express the **average movie duration in hours and minutes**. Don't use decimals.
+select floor(avg(length)) as avg_length,
+       floor(avg(length)/60) as avg_lengh_hour,
+       floor(mod(avg(length),60)) as avg_lengh_minute
+from sakila.film;
+
+# Calculate the **number of days that the company has been operating**.
+select max(rental_date),
+       min(rental_date),
+       DATEDIFF(max(rental_date),min(rental_date)) as total_operation_days
+from sakila.rental;
+
+# retrieve rental information and add two additional columns to show the **month and weekday of the rental**. Return 20 rows of results.
+create table rental_month_weekday
+select *,
+       date_format(rental_date,'%M') as rental_month,
+       date_format(rental_date,'%W') as rental_weekday
+from sakila.rental
+limit 20;
+
+# Retrieve rental information and add an additional column called `DAY_TYPE` with values **'weekend' or 'workday'**, depending on the day of the week
+select *, 
+       case when rental_weekday in ('SATURDAY','SUNDAY') THEN 'weekend'
+       else 'workday'
+       end as DAY_TYPE
+from rental_month_weekday;
+
+
+# retrieve the **film titles and their rental duration**as
+select title,
+	   coalesce(rental_duration,'Not Available') as film_rental_duration
+from sakila.film
+order by title asc;
+
+# retrieve the **concatenated first and last names of customers**, along with the **first 3 characters of their email** address
+# The results should be ordered by last name in ascending order to make it easier to use the data.*
+select concat(first_name,' ',last_name) as Customer_Name,
+	   left(email,3) as email_first3_char
+from sakila.customer
+order by last_name asc;
+
+# The **total number of films** that have been released.
+select count(*) as total_num_films
+from sakila.film;
+
+# The **number of films for each rating**.
+# sorting** the results in descending order of the number of films.
+select rating, count(*) as total_num_films_byRating
+from sakila.film
+group by rating
+order by total_num_films_byRating desc;
+
+# The **mean film duration for each rating**, and sort the results in descending order of the mean duration. 
+create table avg_film_duration_rating as
+select rating,round(avg(length),2) as avg_film_duration
+from sakila.film
+group by rating
+order by avg_film_duration desc;
+
+# Identify **which ratings have a mean duration of over two hours** 
+select rating,round(avg(length),2) as avg_film_duration
+from sakila.film
+group by rating
+having round(avg(length),2) > 120;
+
+
+# determine which last names are not repeated in the table `actor`.
+select last_name
+from actor
+group by last_name
+having count(*) = 1