SQL Dynamically Joining Tables on Various Columns - sql

Question

First time posting!
Have a use case where we want to join some sales data to a master agreement table to determine applicable fee's at a transactional level.
The hard part is that the agreement table has VARIOUS possibilities, and in a worse case scenario at least a "catch all".
We would want to start at the *most granular" level. So the purple line matches on all possible values.
However, a field like the blue sales record does not match on any value to the master except supplier, so in that case it is a catch all.
I've thought of concat'ing all the rows in the master, but then I'd need to find a way of joining it to sales? a simple concat would not successfully join the blue row example together. So it's like the join would have to dynamically choose which columns to compare.
By chance would any users have some idea's on how to achieve this?
Thanks!
(Code for tables)
create TABLE T_TEST_AGREEMENT (
SUPPLIER VARCHAR(254),
ITEM VARCHAR(254),
PROGRAM INT,
RXDA VARCHAR(254),
CTRCT INT,
FEE INT
);
create TABLE T_TEST_AGREEMENT_SALES (
SUPPLIER VARCHAR(254),
ITEM VARCHAR(254),
PROGRAM INT,
RXDA VARCHAR(254),
CTRCT INT
);
INSERT INTO T_TEST_AGREEMENT values
(123, 'A', 60, 'Y', 4, 1),
(123, 'A', 61, 'N', 4, 2),
(123, 'B', 62, null, 5, 3),
(123, 'C', null, 'Y', 6, 4),
(123, null, 63, null, null, 5),
(123, null, null, 'Y', null, 6),
(123, null, null, null, null, 7);
INSERT INTO T_TEST_AGREEMENT_SALES values
(123, 'D', 63, null, null),
(123, 'F', null, null, null),
(123, 'A', 61, 'N', 4),
(123, 'C', null, 'Y', 6);

Answer 1

You can use a correlated subquery:
select st.*,
(select m.fee
from master m
where m.supplier = st.supplier and
(m.item is null or m.item = st.item) and
(m.program is null or m.program = st.program) and
(m.rxda is null or m.rxda = st.rxda) and
(m.ctrct is null or m.ctrct = st.ctrct)
order by ( (case when m.item = st.item then 1 else 0 end) +
(case when m.program = st.program then 1 else 0 end) +
(case when m.rxda = st.rxda then 1 else 0 end) +
(case when m.ctrct = st.ctrct then 1 else 0 end) +
) desc
fetch first 1 row only
) as fee
from sales_transactions st;
This uses standard SQL syntax. It might vary depending on your row.