Last tested: March 2021
MD5 is just a hash that turns strings into hashes.
It's useful for making IDs out of a concatenation of several fields, which makes it valuable for joins. Looker uses it in symmetric aggregates.
Example:
select md5('Amazon Redshift');
md5
----------------------------------
f7415e33f972c03abd4f3fed36748f7a
(1 row)
This content is subject to limited support.
In addition to the linked community article on symmetric aggregates, there is an explanation of why symmetric aggregates look complicated here: https://cloud.google.com/looker/docs/best-practices/understanding-symmetric-aggregates#3