Database agnostic auditing Background

Various databases have custom implementations for auditing:


SQL Server Audit
Oracle Audit
PostgreSQL Audit Trigger
MySQL Enterprise Audit


Problem

A number of problems exist:


There is no consistency (different commands, different log formats, etc.)
There does not appear to be an ANSI SQL standard
Some of the audits log to files, rather than a table or tables


Question

What ANSI SQL table auditing mechanism is:


database agnostic; and
tracks changes that can be queried using SQL (i.e., an audit table, not a log file)?


If no ANSI SQL standard for audit tables exists, then what alternatives exist for database-agnostic auditing (e.g., create a custom audit table) of CRUD operations against all tables in a schema?
Triggers make an auditing mechanism, that satisfies your criteria.


they are present in the ISO/ANSI standard (ISO 9075)
they can be used to track row-level changes
they can save data to tables, hence can be queried using SQL


Only thing I do not understand in your question is "database agnostic" - what does it mean, precisely?