SQL Select rows where col1 or col2 equals variable - mysql

Question

So I want to select rows from table where col1 or col2 equals to variable, but if there is already row selected where col1 equals to variable (variable X) and col2 is anything else (variable Y) then it won't select another row where col2 equals to variable X and col1 equals to that variable Y. Everything ordered by column TIME descending.
Let's say this is my table:
COL1 COL2 TIME COL4
1 2 0 A
1 2 1 B
2 1 2 C
1 3 3 D
3 1 4 E
4 2 5 F
3 4 6 G
1 2 7 H
4 1 8 I
And let's say that variable X equals to 1, then I want to have these rows:
COL1 COL2 TIME COL4
4 1 8 I
1 2 7 H
3 1 4 E
So it won't show me this row
COL1 COL2 TIME COL4
2 1 2 C
because there is already a combination where col1/col2 is 2/1 or 1/2.
Sorry if I explained it in a bad way, but I can't think of better explanation.
Thank you guys.

Answer 1

Making a couple of key assumptions...
SELECT a.*
FROM my_table a
JOIN
( SELECT MAX(time) time
FROM my_table
WHERE 1 IN (COL1,COL2)
GROUP
BY LEAST(col1,col2)
, GREATEST(col1,col2)
) b
ON b.time = a.time;

Answer 2

EDIT: I posted this answer when it was thought that OP's database was SQL Server. But as it turns out, the database is MySQL.
I think this query should do it:
select t.col1, t.col2, t.time, t.col4
from (select t.*,
row_number() over (
partition by
case when col1 < col2 then col1 else col2 end,
case when col1 < col2 then col2 else col1 end
order by time desc) as rn
from tbl t
where t.col1 = x or t.col2 = x) t
where t.rn = 1
order by t.time desc
The key part is defining the row_number partition by clause in such a way that (1, 2) is considered equivalent to (2, 1), which is what the case statements do. Once the partitioning works correctly, you just need to keep the first row of every "partition" (where t.rn = 1) to exclude duplicate rows.