The refresh of IOx added SQL capability and infinite cardinality while also handling bigger data sets. Additionally, it offers faster data retrieval, the most important aspect of the update ...

9 best practices for faster SQL queries Retrieve only the columns you need Use CASE instead of UPDATE for conditional column updates Keep large-table queries to a minimum Pre-stage your data ...

One will update all the rows in a, and the other will only update matching rows. Depending on your schema, that might be fine, but as others have mentioned, it might trip all of your timestamps.