*** Technical Assessment ****
Table schema
ORDERS
order_id varchar(30) composite primary key
customer_id numeric(38,0)
order_datetime timestamp
item_id varchar(10) composite primary key
order_quantity numeric(38,0)
Sample extract from ORDERS

order_id | customer_id | order_datetime | item_id | order_quantity

A-001 | 32483 | 2018-12-15 09:15:22 | B000 | 3
A-005 | 21456 | 2019-01-12 09:28:35 | B001 | 1
A-005 | 21456 | 2019-01-12 09:28:35 | B005 | 1
A-006 | 42491 | 2019-01-16 02:52:07 | B008 | 2

ITEMS
item_id varchar(10) primary key
item_category varchar(20)
Sample extract from ITEMS

item_id | item_category

B000 | Outdoors
B001 | Outdoors
B002 | Outdoors
B003 | Kitchen
B004 | Kitchen

/* Questions */
-- Q1: How many UNITS have been ordered yesterday? UNITS is the total quantity ordered.
-- Output as: Units

-- Q2: How many UNITS have been ordered in the last 7 days (including today) in EACH and EVERY category? Please consider SEVEN calendar days in total, including today.
-- Please consider ALL categories, even those which have zero orders.
-- Output as: Category | Units

-- Q3: How many UNITS in EACH and EVERY category have been ordered on each day of the week in the last 7 days (including today)?
-- Output as: Category | Sunday_units | Monday_units | Tuesday_units | Wednesday_units | Thursday_units | Friday_units | Saturday_units

-- Q4: It is possible for customers to place multiple orders on a single date.
-- For ALL customers, write a query to get the earliest ORDER_ID for each customer for each date they placed an order.
-- Output as: Customer_id | Order_date | First_order_id

-- Q5: Write a query to get the second earliest ORDER_ID for each customer for each date they placed AT LEAST two orders.
-- Output as: Customer_id | Order_date | Second_order_id