The database I spend the most time in these days is Snowflake, the cloud based data warehouse. It still has a schema, but doesn’t have indices or constraints in the same way that MySQL or PostgreSQL does.
Yesterday, I needed to fix some data quality problems anyway. The prompt pushed me an extra bit to write dbt tests as I was making the fixes. There are built-in tests to emulate null or foreign key constraints, but there are also singular tests that can be specific to particular tables and columns. They are implemented as a query that returns any “failing” rows, which were ideal for the changes I needed to make.