How to select rows with conditional values of one column in SQL - sql

Question

Say I have this table:
id
timeline
1
BASELINE
1
MIDTIME
1
ENDTIME
2
BASELINE
2
MIDTIME
3
BASELINE
4
BASELINE
5
BASELINE
5
MIDTIME
5
ENDTIME
6
MIDTIME
6
ENDTIME
7
RISK
7
RISK
So this is what the data looks like except the data has more observations (few thousands)
How do I get the output so that it will look like this:
id
timeline
1
BASELINE
1
MIDTIME
2
BASELINE
2
MIDTIME
5
BASELINE
5
MIDTIME
How do I select the first two terms of each ID which has 2 specific timeline values (BASELINE and MIDTIME)? Notice id 6 has MIDTIME and ENDTIME,and id 7 has two RISK I don't want these two ids.
I used
SELECT *
FROM df
WHERE id IN (SELECT id FROM df GROUP BY id HAVING COUNT(*)=2)
and got IDs with two timeline values (output below) but don't know how to get rows with only BASELINE and MIDTIME.
id timeline
---|--------|
1 | BASELINE |
1 | MIDTIME |
2 | BASELINE |
2 | MIDTIME |
5 | BASELINE |
5 | MIDTIME |
6 | MIDTIME | ---- dont want this
6 | ENDTIME | ---- dont want this
7 | RISK | ---- dont want this
7 | RISK | ---- dont want this
Many Thanks.

Answer 1

You can try using exists -
DEMO
select * from t t1 where timeline in ('BASELINE','MIDTIME') and
exists
(select 1 from t t2 where t1.id=t2.id and timeline in ('BASELINE','MIDTIME')
group by t2.id having count(distinct timeline)=2)
OUTPUT:
id timeline
1 BASELINE
1 MIDTIME
2 BASELINE
2 MIDTIME
5 BASELINE
5 MIDTIME

Answer 2

I think this query should give you the result you want.
NOTE: As i understand, you don't want the ID where exists a "ENDTIME", and in your sample data, there is an "ENDTIME" for ID 1. I assumed this was an error so i made a query that excludes all id containing "ENDTIME".
WITH CTE AS
(
SELECT
id
FROM
df
WHERE
timeline IN ('ENDTIME', 'RISK')
)
SELECT
id,
timeline
FROM
df
WHERE
id NOT IN (SELECT id FROM CTE);

Answer 3

There's probably a number of ways to do this, here's one way that will pick up BASELINE and MIDTIME rows where only they exist, ensuring there are only 2 rows per returned ID. Without knowing the ordering of timeline, it's not possible to go further I don't think:
SELECT
id
, timeline
FROM (
SELECT
*
, SUM(CASE WHEN timeline = 'BASELINE' THEN 1 ELSE 0 END) OVER (PARTITION BY id) AS BaselineCount
, SUM(CASE WHEN timeline = 'MIDTIME' THEN 1 ELSE 0 END) OVER (PARTITION BY id) AS MidtimeCount
FROM df
WHERE df.timeline IN ('BASELINE', 'MIDTIME')
) subquery
WHERE subquery.BaselineCount > 0
AND subquery.MidtimeCount > 0
GROUP BY
id
, timeline
;