Why am I getting syntax error in SQL Server 'in' clause? - sql

Question

I have written a query in SQL Server and am getting an error.
Code:
with cte as (
select pe1.name as P1,
pe2.name as P2,
m.title as T
from participant pa1
join participant pa2 on pa2.idMeeting = pa1.idMeeting
and pa2.idPerson > pa1.idPerson
join person pe1 on pe1.id = pa1.idPerson
join person pe2 on pe2.id = pa2.idPerson
join meeting m on m.id = pa1.idMeeting
),
cte_meet_max as (
select count(*) cnt, P1,P2
from cte
group by P1,P2
)
select *
from cte
where (P1,P2) in (
select P1,P2
from cte_meet_max
where cnt = (select max(cnt) from cte_meet_max)
);
Error:
Msg 4145, Level 15, State 1, Line 25
An expression of non-boolean type specified in a context where a condition is expected, near ','.
Desired result:
Can we put two columns with 'in' clause in SQL Server?
Please help.
Thanks in advance.
Note: I tried solving the question posted before question

Answer 1

An EXISTS condition is the proper way to rewrite this in SQL Server:
with cte as (
select pe1.name as P1,
pe2.name as P2,
m.title as T
from participant pa1
join participant pa2 on pa2.idMeeting = pa1.idMeeting
and pa2.idPerson > pa1.idPerson
join person pe1 on pe1.id = pa1.idPerson
join person pe2 on pe2.id = pa2.idPerson
join meeting m on m.id = pa1.idMeeting
),
cte_meet_max as (
select count(*) cnt, P1,P2
from cte
group by P1,P2
)
select *
from cte
where exists (
select *
from cte_meet_max m1
where m1.cnt = (select max(m2.cnt) from cte_meet_max m2)
and m1.p1 = cte.p1
and m1.p2 = cte.p2
)

Answer 2

Optional solution:
I used detail from both questions here.
Thanks to #Sander for the initial test case. I've made a tiny change to insert the missing meeting (id = 500), in case someone wanted to join with that table, and I've created a fiddle to show the test case:
Working Test Case for SQL Server
The solution counts the meetings each pair of participants have in common.
Additionally, I use a window function to, in the same query expression, find the MAX count over the entire set of results, avoiding one separate step.
As a result, the last query expression only needs to compare the current cnt to the max_cnt, available in each row, without needing correlated behavior.
Most are assuming the person names are unique. I also made that assumption in the first query, but used the primary keys (or would have been PKs, if constraints were created) in the second query.
WITH cte AS (
SELECT pe1.name as p1
, pe2.name as p2
, COUNT(*) AS cnt
, MAX(COUNT(*)) OVER () AS max_cnt
FROM participant pa1
JOIN participant pa2
ON pa2.idMeeting = pa1.idMeeting
AND pa2.idPerson > pa1.idPerson
JOIN person pe1 on pe1.id = pa1.idPerson
JOIN person pe2 on pe2.id = pa2.idPerson
GROUP BY pe1.name, pe2.name
)
SELECT *
FROM cte
WHERE cnt = max_cnt
;
If we don't need person names, we can avoid a little work:
WITH cte AS (
SELECT pa1.idPerson as p1
, pa2.idPerson as p2
, COUNT(*) AS cnt
, MAX(COUNT(*)) OVER () AS max_cnt
FROM participant pa1
JOIN participant pa2
ON pa2.idMeeting = pa1.idMeeting
AND pa2.idPerson > pa1.idPerson
GROUP BY pa1.idPerson, pa2.idPerson
)
SELECT *
FROM cte
WHERE cnt = max_cnt
;

Answer 3

You should only concatenate P1 and P2 in you're where clause
with cte as (
select pe1.name as P1,
pe2.name as P2,
m.title as T
from participant pa1
join participant pa2 on pa2.idMeeting = pa1.idMeeting
and pa2.idPerson > pa1.idPerson
join person pe1 on pe1.id = pa1.idPerson
join person pe2 on pe2.id = pa2.idPerson
join meeting m on m.id = pa1.idMeeting
),
cte_meet_max as (
select count(*) cnt, P1,P2
from cte
group by P1,P2
),
meet_max as (select P1,P2
from cte_meet_max
where cnt = (select max(cnt) from cte_meet_max))
select *
from cte ,meet_max
where cte.P1=meet_max.P1 and cte.P2=meet_max.P2
);