Join two tables on consecutive segments - sql

Question

I want to join two tables, where the first table has more entries than the second, such that rows from each are joined in order. Maybe a little example would be helpful:
Table T:
| tid | sid | ron | val | seqno |
| --- | --- | --- | --- | --- |
| 1 | a | x1 | 15 | 1 |
| 2 | b | x2 | 10 | 3 |
| 2 | b | x3 | 20 | 4 |
| 3 | a | x5 | 10 | 5 |
| 4 | c | x9 | 15 | 7 |
| 4 | c | x9 | 15 | 8 |
| 4 | c | x9 | 20 | 10 |
| 4 | c | x9 | 15 | 11 |
| 6 | b | x11 | 22 | 12 |
| 7 | b | x12 | 10 | 14 |
| 7 | b | x13 | 10 | 16 |
| 7 | b | x13 | 10 | 17 |
| 7 | b | x14 | 10 | 19 |
The second table (Table C) is as follows (in reality, more columns):
| tid | sid | ron | val | fid |
| --- | --- | --- | --- | --- |
| 2 | b | x3 | 20 | 54 |
| 4 | c | x9 | 15 | 12 |
| 4 | c | x9 | 15 | 14 |
| 4 | c | x9 | 20 | 15 |
| 4 | c | x9 | 15 | 20 |
| 7 | b | x13 | 10 | 112 |
| 7 | b | x13 | 10 | 113 |
seqNo and fid are there in each table to provide ordering within the groups formed by (tid, sid, ron), and that is the ordering I'd like to maintain.
How can I get from these two tables to something like the following table?
| tid | sid | ron | val | fid | seqno |
| --- | --- | --- | --- | --- | --- |
| 2 | b | x3 | 20 | 54 | 4 |
| 4 | c | x9 | 15 | 12 | 7 |
| 4 | c | x9 | 15 | 14 | 8 |
| 4 | c | x9 | 20 | 15 | 10 |
| 4 | c | x9 | 15 | 20 | 11 |
| 7 | b | x13 | 10 | 112 | 16 |
| 7 | b | x13 | 10 | 113 | 17 |
I can't assign a rank to each element in the group and use that for matching inside of a LEFT JOIN, since there are cases where matching doesn't begin at the end of the group (for example tid=7). Also, because val in the same group may have repeated values, I can't blindly match on it either, as that may blow up the number of rows.

Answer 1

This is what I managed to get late last night, seems to be working correctly:
WITH
table_t AS (
SELECT *
FROM (VALUES
(1,'a','x1',15,1),
(2,'b','x2',10,3),
(2,'b','x3',20,4),
(3,'a','x5',10,5),
(4,'c','x9',15,7),
(4,'c','x9',15,8),
(4,'c','x9',20,10),
(4,'c','x9',15,11),
(6,'b','x11',22,12),
(7,'b','x12',10,14),
(7,'b','x13',10,16),
(7,'b','x13',10,17),
(7,'b','x14',10,19)
) AS c(tid, sid, ron, val, seq)
),
table_t_ranked AS (
SELECT *
, DENSE_RANK() OVER (PARTITION BY tid, sid, ron ORDER BY seq ASC) AS ranking
FROM table_t
),
table_c AS (
SELECT *
FROM (VALUES
(2,'b','x3',20,54),
(4,'c','x9',15,12),
(4,'c','x9',15,14),
(4,'c','x9',20,15),
(4,'c','x9',15,20),
(7,'b','x13',10,112),
(7,'b','x13',10,113)
) AS c(tid, sid, ron, val, fid)
),
table_c_ranked AS (
SELECT *
, DENSE_RANK() OVER (PARTITION BY tid, sid, ron ORDER BY fid ASC) AS ranking
FROM table_c
),
foo AS (
SELECT c.*
, t.seq
, t.ranking as ranking_t
FROM table_c_ranked c
LEFT JOIN table_t_ranked t
ON c.tid = t.tid
AND c.sid = t.sid
AND c.ron = t.ron
AND c.val = t.val
)
SELECT tid, sid, ron, val, fid, seq
FROM foo
WHERE ranking = ranking_t
ORDER BY tid, seq