(CockroachDB CTO here) We haven't implemented everything in the standard yet (Nor will we by 1.0 - there's a lot of stuff there!), but we are aiming to ultimately be compliant with the SQL standard. For example, when we introduced "time travel queries" (https://www.cockroachlabs.com/blog/time-travel-queries-selec...) we adopted the SQL-standard syntax "AS OF SYSTEM TIME" (as opposed to the non-standard out-of-band parameter used in Cloud Spanner)