Calculating/Categorizing/Sorting

Raw Data

 

 

Calculating ( + )

 

Not only addition but also multiplication and division are possible.

select food_preparation_time,
       delivery_time,
       food_preparation_time + delivery_time as total_time
from food_orders

 

 

result

 

 

 

Sum & Average

select sum(food_preparation_time) total_food_preparation_time,
       avg(delivery_time) avg_delivery_time
from food_orders

 

 

 

 

Count

By adding COUNT(1) or (*), you can count the number of rows for all columns. Adding DISTINCT allows you to count the number of distinct values for a specific column.

 

select count(1) count_of_orders,
       count(distinct customer_id) count_of_customers
from food_orders

 

 

Max / Min

 

select min(price) min_price,
       max(price) max_price
from food_orders

 

 

 

Group By / Order By

* "GROUP BY" and "SELECT BY" statements come after "SELECT", "FROM", and "WHERE"

 

"GROUP BY" is used to create categories, while "ORDER BY" is used for sorting.

 

 

Practice

Retrieve the highest and lowest order amounts for each type of food, and sort them in ascending order by the lowest order amount.

SELECT cuisine_type, MIN(price) min_price, max(price) max_price 
from food_orders
group by cuisine_type 
order by min(price) desc

 

Result