MySQL overlaping time periods based on criteria - mysql

Question

i am trying to write a query which would show me all records which overlap based on values Valid_From and Valid_To and based on criteria.
This is my sample data:
ID | Valid_From | Valid_To | Block_Type | Valid | Block_ID
1 5 10 a TRUE 1
2 10 15 a TRUE 1
3 6 10 a TRUE 1
4 3 4 a FALSE 1
5 2 4 a FALSE 1
6 1 1 a FALSE 1
7 1 10 b TRUE 1
8 1 10 c TRUE 2
9 1 10 c TRUE 2
10 1 15 b TRUE 1
11 5 10 a TRUE 1
ID is Primary Key with Auto Increment - unique for every record
Block_Type - Type of block - can have more values for every Block_ID example: Block_ID 1 has Block_Type "a" and "b", Block_ID 2 has Block_Type "c", every Block_ID can have any Block_Type, meaning every Block_ID can have Block_Type "a" to "z"
Valid - this just states if Valid_To is bigger than some value, for
testing i set this value to 5
Block_ID - groups multiple records in one Group
For showing what records overlap i use this query:
select a.id, GROUP_CONCAT(b.id) as abcd
from new_table a, new_table b
where a.id <> b.id
and a.Block_ID = b.Block_ID
and a.Block_Type = b.Block_Type
and a.Valid = b.Valid
and ((a.Valid_To between b.Valid_From and b.Valid_To) or (a.Valid_From between b.Valid_From and b.Valid_To)
or (a.Valid_To = b.Valid_From) or (a.Valid_From = b.Valid_To))
group by a.id;
this works fine, it shows me if any records with same Block_Type, same value in Valid and Block_ID overlap, my problem is that this query doesnt show me records which dont overlap (in this example it is record with ID 6) i completely understand why, so i tried to edit my query using case when instead of where but so far i wasnt able to achieve what i want.
This is what my query returns now:
ID | abcd
1 2
2 1,11,3
3 2
4 5
5 4
7 10
8 9
9 8
10 7
11 2
I would like this query to list all records and to list in new column "abcd" all overlaping records, for records that do not overlap i would just like null in the same column, so it would look like this:
ID | abcd
1 2
2 1,11,3
3 2
4 5
5 4
6 null
7 10
8 9
9 8
10 7
11 2
cant you point me in the right direction? What can i change to make it work the way i need?
Thank you very much

Answer 1

If i understand your problem correctly, You need a left join instead of Inner join -
SELECT a.id, GROUP_CONCAT(b.id) AS abcd
FROM new_table a
LEFT JOIN new_table b ON a.id <> b.id
AND a.Block_ID = b.Block_ID
AND a.Block_Type = b.Block_Type
AND a.Valid = b.Valid
AND ((a.Valid_To BETWEEN b.Valid_From AND b.Valid_To)
OR (a.Valid_From BETWEEN b.Valid_From AND b.Valid_To)
OR (a.Valid_To = b.Valid_From)
OR (a.Valid_From = b.Valid_To)
)
GROUP BY a.id;