Compare rows with condition - sql

Question

Edit: when 5 or 9 does not exist, i need a null value (or another flag)
I have 3 columns. SECTION, STATUS and NAME. Within a SECTION there are a maximum of 10 rows (STATUS 1 to 10). I have to compare the value of NAME for STATUS 5 and 9 within a SECTION. AND then indicate if those 2 NAMES (for STATUS 5 and 9) are the same for each SECTION.
section status name
1 5 a
1 6 a
1 9 b
2 4 c
2 5 d
2 9 d
2 10 d
3 5 e
3 10 e
Desired output
Section equalnames
1 no
2 yes
3 null/flag

Answer 1

select
a.section,
case
when a.name = b.name then 'YES'
when a.name <> b.name then 'NO'
when (a.name is null or b.name is null) then 'NULL' end
from
(select * from <table> where status = 5) a
full join (select * from <table> where status = 9) b
on a.section = b.section

Answer 2

With conditional aggregation:
SELECT section,
MAX(CASE WHEN status = 5 THEN name END) =
MAX(CASE WHEN status = 9 THEN name END) equalnames
FROM tablename
WHERE status IN (5, 9)
GROUP BY section
ORDER BY section
See the demo.
Results:
section | equalnames
------- | ----------
1 | f
2 | t
3 | null

Answer 3

You could try using a left join on same table for 5 and 9
select a.section, a.status s5, a.name n5, b.status b9, b.name n9
, case when a.name = b.name the yes
when a.name is null or b.name is nul the NULL
when a.name <> b.name then no end equalname
from my_table a
left join my_table b a.section = b.section and a.status =5 and b.status=9

Answer 4

A more optimised solution could be with cte and window function:
with cte as (
select section, count(status)over(partition by section,name order by section) count_with_same_name,
count(status)over(partition by section order by section) count_with_different_name
from tname where status in (5,9))
select section,(case when (max(count_with_same_name)=2) then 'Yes' when (max(count_with_different_name)=2) then 'No' else 'null/flag' end)
from cte
group by section
Output:

Answer 5

I think you just want conditional aggregation:
select section,
(case when min(case when status = 5 then name end) =
min(case when status = 9 then name end)
then 'yes'
when count(case when status in (5, 9) then status end) < 2
then 'null/flag'
else 'no'
end)
from t
group by section;
No join is needed and I would not advise one for this problem.