Farid Zidan <farid@zidsoft.com> wrote:
    

If we were strictly complying with the SQL standard,
      

Considering the statement works in all the 9 DBMS systems+ that I
have tested so far as mentioned above, I would say PostgreSQL is
not compliant with SQL standard in this regard.
    

 
The SQL standard is a document published by the International
Standards Organization (ISO) and also adopted by the American
National Standards Institute (ANSI).  Those documents don't require
a query in either of the forms you presented to work.  Because of
the convenience factor, most database products have non-standard
extensions to omit type specification in some places.  PostgreSQL's
extensions are oriented more toward user-installable data types
(such as geometric shapes or global coordinates), so the particulars
of our non-standard extensions differ so that use of those features
is as easy as practicable.  That does result in some non-standard
extensions which work in other products not working in PostgreSQL. 
 
I think you'll find that the syntax I suggested (using the standard
timestamp literal instead of a bare character string literal) will
work in all of the databases you mentioned; if you want portable
code, it is best to follow the standard rather than some inferred
popular convention.
 
I hope this helps.
 
-Kevin