Solution1: (Union)
(select employee_id, department_id
from employee
where primary_flag = "Y")
union
(select employee_id, department_id
from employee
group by employee_id
having count(employee_id) = 1)
Solution2: (Window Function)
select t.employee_id, t.department_id
from (select *, count(employee_id) over(partition by employee_id) as C
from employee) t
where t.C = 1 or t.primary_flag = "Y"
Solution3: (coalesce) (case when then else end) (if)
select employee_id, coalesce(max(case when primary_flag = "Y" then department_id else null end), department_id) department_id
from employee
group by employee_id
select employee_id,coalesce(max(if(primary_flag = "Y", department_id, null)), department_id) department_id
from employee
group by employee_id
Solution 1: (UNION)
(select product_id, "store1" as store, store1 as price
from Products
where store1 is not null)
union
(select product_id, "store2" as store, store2 as price
from Products
where store2 is not null)
union
(select product_id, "store3" as store, store3 as price
from Products
where store3 is not null)
Solution 2: (UNPIVOT) (MS SQL)
select product_id,store,price
from Products
UNPIVOT
(
price
for store in (store1,store2,store3)
) as T
Solution 1: (left join) (ifnull)
select Q.id as id, Q.year as year, ifnull(N.npv,0) as npv
from Queries as Q left join NPV as N on (Q.id = N.id and Q.year = N.year)
Solution 2: (left join) (coalesce)
select Q.id as id, Q.year as year, coalesce(N.npv,0) as npv
from Queries as Q left join NPV as N on (Q.id = N.id and Q.year = N.year)
SELECT distinct session_id
FROM playback pb LEFT JOIN ads ad
ON pb.customer_id = ad.customer_id
AND ad.timestamp BETWEEN start_time and end_time
WHERE ad.customer_id IS NULL