Question

What is the difference between CHECKSUM_AGG() and CHECKSUM() ?

Answer 1

• CHECKSUM calculates a hash for one or more values in a single row and returns an integer.
• CHECKSUM_AGG is an aggregate function that takes a single integer value from multiple rows and calculates an aggregated checksum for each group.

They can be used together to checksum multiple columns in a group:

SELECT category, CHECKSUM_AGG(CHECKSUM(*)) AS checksum_for_category
FROM yourtable
GROUP BY category