SELECT is ANSI SQL:2011-compliant with extensions.
In Teradata SQL, the FROM clause is optional. This is a Teradata extension to the ANSI SQL:2011 standard, in which a FROM clause is mandatory.
The WITH, SAMPLE, QUALIFY, and TOP clauses are Teradata extensions to the ANSI SQL:2011 standard.
The documented syntax specifies the ANSI SQL:2011 ordering of these clauses: FROM, WHERE, GROUP BY, HAVING, and ORDER BY. Teradata Database does not enforce this ordering, but you should observe it when you write applications to maintain ANSI compliance.