Join on a selected number of digits - sql

Question

The column ddm_zip has only 5 digit zipcodes. The column tt_pad_zip contains values anywhere between 2-5. I would like to perform a join selecting values that appear on both sides of the table.
However, tt_pad_zip has various levels of granularity.
For e.g. when we see value of 55 in tt_pad_zip, it is considering all zipcodes that start with 55, for e.g. 551...553...55636 etc. Hence I want the join to select this.
For e.g. when we see value of 558 in tt_pad_zip, it is considering all zipcodes that start with 558, for e.g. 5581...5585...558743 etc. Hence I want the join to select this.
However if there is a value in tt_pad_zip that has the exact zipcode as ddm_zip e.g. 58636 as shown below, I would like the output to pick this .
column: ddm_zip column: tt_pad_zip
55636 55
57254 5734
58636 57254
58636

Answer 1

Join on the SUBSTRing of ddm_zip that has equal length to the tt_pad_zip value you are comparing it to. Either:
SUBSTR( ddm_zip, 1, LENGTH( tt_pad_zip ) ) = tt_pad_zip
or:
ddm_zip LIKE tt_pad_zip || '%'
Oracle Setup:
CREATE TABLE table1 ( ddm_zip ) AS
SELECT '55636' FROM DUAL UNION ALL
SELECT '57254' FROM DUAL UNION ALL
SELECT '55824' FROM DUAL;
CREATE TABLE table2 ( tt_pad_zip ) AS
SELECT '55' FROM DUAL UNION ALL
SELECT '5734' FROM DUAL UNION ALL
SELECT '57254' FROM DUAL UNION ALL
SELECT '55636' FROM DUAL;
Query:
SELECT *
FROM table1 t1
INNER JOIN
table2 t2
ON t1.ddm_zip LIKE t2.tt_pad_zip || '%'
Output:
DDM_ZIP | TT_PAD_ZIP
:------ | :---------
55636 | 55
55636 | 55636
57254 | 57254
55824 | 55
Query 2: If you want the most granular match.
SELECT DDM_ZIP,
MAX( TT_PAD_ZIP ) AS TT_PAD_ZIP
FROM table1 t1
INNER JOIN
table2 t2
ON t1.ddm_zip LIKE t2.tt_pad_zip || '%'
GROUP BY DDM_ZIP
Output:
DDM_ZIP | TT_PAD_ZIP
:------ | :---------
55636 | 55636
57254 | 57254
55824 | 55
db<>fiddle here

Answer 2

I think you are looking for something like the following:
-- Sample Data:
WITH dat (ddm_zip, tt_pad_zip) AS
(SELECT 0,55 FROM dual
UNION ALL
SELECT 1,5734 FROM dual
UNION ALL
SELECT 2,57254 FROM dual
UNION ALL
SELECT 3,55636 FROM dual
UNION ALL
SELECT 55636, 99 FROM dual
UNION ALL
SELECT 57254, 88 FROM dual
UNION ALL
SELECT 57341, 77 FROM dual)
-- Query:
SELECT d2.ddm_zip, d1.tt_pad_zip
FROM dat d1
JOIN dat d2
-- Join the data via like:
ON d2.ddm_zip LIKE d1.tt_pad_zip || '%'
-- Exclude the data where a "better" match exists:
AND NOT EXISTS (SELECT 1 FROM dat d3
WHERE d2.ddm_zip LIKE d3.tt_pad_zip || '%'
AND LENGTH(d1.tt_pad_zip) < LENGTH(d3.tt_pad_zip))

Answer 3

You can use conditional join with a CASE statement in the ON clause:
select t1.ddm_zip, t2.tt_pad_zip
from table1 t1 inner join table2 t2
on t1.ddm_zip like case
when exists(select 1 from table2 where tt_pad_zip = t1.ddm_zip) then t2.tt_pad_zip
else '%' || t2.tt_pad_zip || '%'
end
See the demo.
Results:
> DDM_ZIP | TT_PAD_ZIP
> :------ | :---------
> 55636 | 55
> 57254 | 57254
> 58636 | 58636

Answer 4

You could try using the SUBSTR operation to just compare the first two numbers of each column. I don't know which type of join you want, your table names, or example data, but here is a good syntax.
SELECT
*
FROM
table1 INNER JOIN table2 ON SUBSTR(ddm_zip, 1, 2) = SUBSTR(tt_pad_zip, 1,2)