mas-tono / japanese-restaurant

analyzing japanese restaurant business performance

japanese-restaurant

analyzing japanese restaurant business performance

using MS. SQL SERVER STUDIO

SQL project/case study from: https://8weeksqlchallenge.com/case-study-1/

steps:

1. import all csv files into SQL SERVER

2. data checking

3. analysis:

   1. What is the total amount each customer spent at the restaurant?

      total amount each customer spent

      		
       select s.customer_id, SUM(m.price) as total_spend
       from sales_dannys s
       join menu_dannys m
       on s.product_id = m.product_id
       group by s.customer_id;		
       

      

   2. How many days has each customer visited the restaurant?

      amount of each customer visit

      		
       select customer_id, COUNT(order_date) as cnt_visit
       from sales_dannys 
       group by customer_id;	
       

      

   3. What was the first item from the menu purchased by each customer?

      first item purchased of each customer

      		
       with satu as (select s.customer_id, 
       	s.order_date, 
       	m.product_name, 
       	DENSE_RANK() over(partition by customer_id order by order_date) as rn
       from sales_dannys s
       join menu_dannys m
       on s.product_id = m.product_id),
      
       dua as (select distinct customer_id, product_name
       from satu
       where rn = 1)
      
       select customer_id, STRING_AGG(product_name, ', ') as first_item_purchased
       from dua
       group by customer_id;
       

      

   4. What is the most purchased item on the menu and how many times was it purchased by all customers?

      most purchased item and purchasing amount

      		
       with satu as (select m.product_name, 
       		COUNT(m.product_name) as cnt_prod_name, 
       		RANK() over(order by COUNT(product_name) desc) as rn
       from sales_dannys s
       join menu_dannys m
       on s.product_id = m.product_id
       group by m.product_name)
      
       select product_name, cnt_prod_name
       from satu
       where rn = 1;
       

      

   5. Which item was the most popular for each customer?

      most popular item for each customer

      		
       with satu as (select s.customer_id, 
       	m.product_name, 
       	COUNT(m.product_name) as cnt_item, 
       	RANK() over(partition by s.customer_id order by COUNT(m.product_name) desc) as rn
       from sales_dannys s
       join menu_dannys m
       on s.product_id = m.product_id
       group by s.customer_id, m.product_name)
      
       select customer_id, STRING_AGG(product_name, ', ') as cust_fav_item
       from satu
       where rn = 1
       group by customer_id;
       

      

   6. Which item was purchased first by the customer after they became a member?

      first purchasing after became member

      		
       with satu as (select s.customer_id,
       		s.order_date,
       		m.join_date,
       		me.product_name,
       		RANK() over(partition by s.customer_id order by s.order_date) as rn
       from sales_dannys s
       join members_dannys m
       on s.customer_id = m.customer_id
       join menu_dannys me
       on s.product_id = me.product_id
       where s.order_date >= m.join_date)
      
       select customer_id, order_date, join_date, product_name
       from satu
       where rn = 1;
       

      

   7. Which item was purchased just before the customer became a member?

      item purchased just before the customer became a member

      		
       with satu as (select s.customer_id,
       	s.order_date,
       	m.join_date,
       	me.product_name,
       	dense_rank() over(partition by s.customer_id order by s.order_date) as rn
       from sales_dannys s
       join members_dannys m
       on s.customer_id = m.customer_id
       join menu_dannys me
       on s.product_id = me.product_id
       where s.order_date < m.join_date),
      
       dua as (select customer_id, MAX(rn) as rn_just_before
       from satu
       group by customer_id)
      
       select satu.customer_id, 
       	satu.order_date, 
       	satu.join_date, 
       	satu.product_name
       from satu
       join dua
       on satu.customer_id = dua.customer_id
       where satu.rn = dua.rn_just_before;
       

      

   8. What is the total items and amount spent for each member before they became a member?

      total items and amount spent for each member before they became a member

      		
       with satu as (select s.customer_id,
       	s.order_date,
       	m.join_date,
       	me.product_name,
       	me.price
       from sales_dannys s
       join members_dannys m
       on s.customer_id = m.customer_id
       join menu_dannys me
       on s.product_id = me.product_id
       where s.order_date < m.join_date)
      
       select customer_id, COUNT(product_name) as total_item, SUM(price) as total_spent
       from satu
       group by customer_id;
       

      

   9. If each $1 spent equates to 10 points and sushi has a 2x points multiplier - how many points would each customer have?

      total items and amount spent for each member before they became a member

      
      

      transaction for member only that'll be calculated (only member A & B, and transaction after join membership)

      		
       with satu as (select s.customer_id,
       	s.order_date,
       	m.join_date,
       	me.product_name,
       	me.price,
       	case
       		when me.product_name = 'sushi' then 20 else 10
       	end as point
       from sales_dannys s
       join members_dannys m
       on s.customer_id = m.customer_id
       join menu_dannys me
       on s.product_id = me.product_id
       where s.order_date >= m.join_date)
      
       select customer_id, SUM(price*point) as total_point
       from satu
       group by customer_id;
       

      

   10. In the first week after a customer joins the program (including their join date) they earn 2x points on all items, not just sushi - how many points do customer A and B have at the end of January?

       points customer A and B have at the end of January

       		
       with satu as (select s.customer_id,
       	s.order_date,
       	m.join_date,
       	me.product_name,
       	me.price,
       	case
       		when me.product_name = 'sushi' then 20 else 10
       	end as point,
       	DATEADD(day, 7, m.join_date) as week_after,
       	case
       		when s.order_date >= m.join_date and s.order_date < DATEADD(day, 7, m.join_date) then 20 else 10
       	end as week_after_point
       from sales_dannys s
       join members_dannys m
       on s.customer_id = m.customer_id
       join menu_dannys me
       on s.product_id = me.product_id
       where s.order_date >= m.join_date)
       
       select customer_id, SUM(price*week_after_point) as total_point_end_of_Jan
       from satu
       where order_date < '2021-01-31'
       group by customer_id;