select unique_id, name from Employees as e

left join EmployeeUNI as u

on e.id = u.id

select p.product_name, s.year, s.price from Sales as s left join Product as p on p.product_id = s.product_id

select V.customer_id, COUNT(V.visit_id) as count_no_trans from Visits V left join Transactions T on V.visit_id = T.visit_id where T.transaction_id IS null group by V.customer_id

SELECT w2.id

FROM Weather w1, Weather w2

WHERE w1.recordDate + INTERVAL 1 DAY = w2.recordDate

AND w2.temperature > w1.temperature;

SELECT

machine_id,

ROUND(AVG(end_time - start_time), 3) AS processing_time

(SELECT

machine_id,

process_id,

MAX(CASE WHEN activity_type = 'end' THEN timestamp END) AS end_time,

MAX(CASE WHEN activity_type = 'start' THEN timestamp END) AS start_time

FROM

Activity

GROUP BY machine_id , process_id) t

GROUP BY machine_id;