Validate information between 2 tables - Oracle SQL - sql

Question

I have 2 tables that I need to validate some information, for example:
Table A (GTM_LICENSE_LINE):
License Nº - License Line Nº
123 - 123_1
123 - 123_2
Table B (GTM_LICENSE_LINE_ITEM):
License Line Nº - Item Nº
123_1 - XXX
However, I need to validate if there are any licenses lines without a Item nº associated (all lines must have only one Item nº).
My expected result would be "1" if the condition is true (all license line have an associated item) or null if the condition is false. I'm trying to use LEFT JOIN w/ GROUP BY but it's not working for me.
SELECT u.GTM_LICENSE_LINE_GID
FROM GTM_LICENSE_LINE I
LEFT JOIN GTM_LICENSE_LINE_ITEM U
ON I.LICENSE_LINE_GID = U.GTM_LICENSE_LINE_GID
WHERE i.LICENSE_GID = 'ELEB.L001'
AND U.GTM_LICENSE_LINE_GID is null
GROUP BY U.GTM_LICENSE_LINE_GID
HAVING COUNT(*) > 0
How can I do this using Oracle SQL? Any suggestions?
Thanks

Answer 1

I think you're probably after something like this:
WITH table1 AS (SELECT 123 License_num, '123_1' license_line_num FROM dual UNION ALL
SELECT 123 License_num, '123_2' license_line_num FROM dual UNION ALL
SELECT 456 License_num, '456_1' license_line_num FROM dual UNION ALL
SELECT 456 License_num, '456_2' license_line_num FROM dual),
table2 AS (SELECT '123_1' license_line_num, 'XXX' item_num FROM dual UNION ALL
SELECT '456_1' license_line_num, 'YYY' item_num FROM dual UNION ALL
SELECT '456_2' license_line_num, 'ZZZ' item_num FROM dual)
SELECT t1.license_num,
t1.license_line_num,
MIN(CASE WHEN t2.license_line_num IS NULL THEN 0 ELSE 1 END) OVER (PARTITION BY t1.license_num) all_lines_present
FROM table1 t1
LEFT OUTER JOIN table2 t2 ON t1.license_line_num = t2.license_line_num
ORDER BY t1.license_num, t1.license_line_num;
LICENSE_NUM LICENSE_LINE_NUM ALL_LINES_PRESENT
----------- ---------------- -----------------
123 123_1 0
123 123_2 0
456 456_1 1
456 456_2 1
I'm assuming here that there is a unique constraint on table2 where you can have at most one row for each license_line_num.
This works by outer joining the second table to the first (which shouldn't produce any duplicate lines). Then we use a conditional aggregate function (in this case, MIN) to determine that if there is a value from the second table present, we output a 1 otherwise a 0 for each row, before finding the lowest value.
That way, if any of the rows is missing an item row, the lowest value across all rows for each license_num will be 0.
ETA: If you just want a single row per license_num, you can just use a conditional aggregate function instead, e.g.:
WITH table1 AS (SELECT 123 License_num, '123_1' license_line_num FROM dual UNION ALL
SELECT 123 License_num, '123_2' license_line_num FROM dual UNION ALL
SELECT 456 License_num, '456_1' license_line_num FROM dual UNION ALL
SELECT 456 License_num, '456_2' license_line_num FROM dual),
table2 AS (SELECT '123_1' license_line_num, 'XXX' item_num FROM dual UNION ALL
SELECT '456_1' license_line_num, 'YYY' item_num FROM dual UNION ALL
SELECT '456_2' license_line_num, 'ZZZ' item_num FROM dual)
SELECT license_num,
CASE WHEN all_lines_present = 1 THEN 1 END all_lines_present
FROM (SELECT t1.license_num,
MIN(CASE WHEN t2.license_line_num IS NULL THEN 0 ELSE 1 END) all_lines_present
FROM table1 t1
LEFT OUTER JOIN table2 t2 ON t1.license_line_num = t2.license_line_num
GROUP BY t1.license_num)
ORDER BY license_num;
LICENSE_NUM ALL_LINES_PRESENT
----------- -----------------
123
456 1