Obtain Name Column Based on Value - sql

Question

I have a table that calculates the number of associated records that fit a criteria for each parent record. See example below:
note - morning, afternoon and evening are only weekdays
| id | morning | afternoon | evening | weekend |
| -- | ------- | --------- | ------- | ------- |
| 1 | 0 | 2 | 3 | 1 |
| 2 | 2 | 9 | 4 | 6 |
What I am trying to achieve is to determine which columns have the lowest value and get their column name as such:
| id | time_of_day |
| -- | ----------- |
| 1 | morning |
| 2 | afternoon |
Here is my current SQL code to result in the first table:
SELECT
leads.id,
COALESCE(morning, 0) morning,
COALESCE(afternoon, 0) afternoon,
COALESCE(evening, 0) evening,
COALESCE(weekend, 0) weekend
FROM leads
LEFT OUTER JOIN (
SELECT DISTINCT ON (lead_id) lead_id, COUNT(*) AS morning
FROM lead_activities
WHERE lead_activities.modality = 'Call' AND lead_activities.bound_type = 'outbound' AND extract('dow' from created_at) IN (0,1,2,3,4,5) AND (extract('hour' from created_at) >= 0 AND extract('hour' from created_at) < 12)
GROUP BY lead_id
) morning ON morning.lead_id = leads.id
LEFT OUTER JOIN (
SELECT DISTINCT ON (lead_id) lead_id, COUNT(*) AS afternoon
FROM lead_activities
WHERE lead_activities.modality = 'Call' AND lead_activities.bound_type = 'outbound' AND extract('dow' from created_at) IN (0,1,2,3,4,5) AND (extract('hour' from created_at) >= 12 AND extract('hour' from created_at) < 17)
GROUP BY lead_id
) afternoon ON afternoon.lead_id = leads.id
LEFT OUTER JOIN (
SELECT DISTINCT ON (lead_id) lead_id, COUNT(*) AS evening
FROM lead_activities
WHERE lead_activities.modality = 'Call' AND lead_activities.bound_type = 'outbound' AND extract('dow' from created_at) IN (0,1,2,3,4,5) AND (extract('hour' from created_at) >= 17 AND extract('hour' from created_at) < 25)
GROUP BY lead_id
) evening ON evening.lead_id = leads.id
LEFT OUTER JOIN (
SELECT DISTINCT ON (lead_id) lead_id, COUNT(*) AS weekend
FROM lead_activities
WHERE lead_activities.modality = 'Call' AND lead_activities.bound_type = 'outbound' AND extract('dow' from created_at) IN (6,7)
GROUP BY lead_id
) weekend ON weekend.lead_id = leads.id

Answer 1

You can use CASE/WHEN/ELSE to check for the specific conditions and produce different values. For example:
with
q as (
-- your query here
)
select
id,
case
when morning <= least(afternoon, evening, weekend) then 'morning'
when afternoon <= least(morning, evening, weekend) then 'afternoon'
when evening <= least(morning, afternoon, weekend) then 'evening'
else 'weekend'
end as time_of_day
from q