SQL Ch6

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1

select b.name as department, a.name as employee, max(a.salary) as salary
from Employee a
join Department b
on a.departmentid = b.id

2

select (case 
        when mod(id,2)=1 and id =(select count(*) from seat) then id
        when mod(id,2)= 0 then id-1
        else id+1
        end) as id,student from seat
order by id;

3

select score, dense_rank()over(order by score) as rank
from scores

4

SELECT DISTINCT(Num) AS Num 
FROM (SELECT Num,id,lag(id,2) OVER(partition by num order by id) AS id_new FROM logs) A 
WHERE A.id = A.id_new + 2