Data reconciliation between 2 datasets on SQL

Question

image_table

I currently need to find all the differences between a new_master dataset and a previous one using SQL Oracle. The datasets have the same structure and consist of both integers and strings and do not have a unique key id unless I select several columns together. You can see an image at the beginning as image_table. I found online this code and I wanted to ask you if you have any advices.

SELECT n.*
FROM new_master as n
LEFT JOIN old_master as o
ON (n.postcode = o.postcode)
WHERE o.postcode IS NULL
SORT BY postcode

In doing so I should get back all the entries from the new_master that are not in the old one.

Thanks

Answer 1

If you are in an Oracle databse, there are a couple queries that can help you find any differences.

Find any records in OLD that are not in NEW.

SELECT * FROM old_master
MINUS
SELECT * FROM new_master;

Find any records in NEW that are not in OLD.

SELECT * FROM new_master
MINUS
SELECT * FROM old_master;

Count number of items in OLD

SELECT COUNT (*) FROM old_master;

Count number of items in NEW

SELECT COUNT (*) FROM new_master;

The COUNT queries are needed in addition to the MINUS queries in case there are duplicate rows with the same column data.