Grouping based on current timestamp in sql - mysql

Question

Okay So I have a df like this:
MEETING_ID sSTART
322 2021-05-01 23:45:00.000
322 2021-05-03 13:45:00.000
312 2021-05-11 23:45:00.000
312 2021-05-13 23:45:00.000
And all I want is a table that can tell me how many previous meetings have occurred and how many meetings are coming up...
To do this I use the CURRENT_TIMESTAMP function, unsure if this is wrong but here's my query that isnt working... For the purposes of this post let's say current time is 5/2/2021 10:40PM
WITH s AS (
SELECT MEETING_ID,
CASE WHEN sSTART > CURRENT_TIMESTAMP THEN 1
ELSE 0
END PREVIOUS_MEETING,
CASE WHEN sSTART < CURRENT_TIMESTAMP THEN 1
ELSE 0
END UPCOMING_MEETING
FROM df
),
ddd AS (SELECT
MEETING_ID,
COUNT(PREVIOUS_MEETING),
COUNT(UPCOMING_MEETING)
FROM s
GROUP BY MEETING_ID
)
SELECT *
FROM ddd
In the end I want this:
MEETING_ID PREVIOUS_MEETING UPCOMING_MEETING
322 1 1
312 2 0
I'm unsure why this is the case but some explanation would help.

Answer 1

You just want a basic pivot query here:
SELECT
MEETING_ID,
SUM(sSTART > CURRENT_TIMESTAMP) AS PREVIOUS_MEETING,
SUM(sSTART <= CURRENT_TIMESTAMP) AS CURRENT_MEETING
FROM df
GROUP BY
MEETING_ID;
Note that we are summing boolean expressions above, which is valid syntax in MySQL. On other databases, you might have to take conditional counts, something like this:
SELECT
MEETING_ID,
COUNT(CASE WHEN sSTART > CURRENT_TIMESTAMP THEN 1 END) AS PREVIOUS_MEETING,
COUNT(CASE WHEN sSTART <= CURRENT_TIMESTAMP THEN 1 END) AS CURRENT_MEETING
FROM df
GROUP BY
MEETING_ID;