Where to find tutorials on portable SQL for PHP and (MySql Oracle PostgreSQL MS SQL)

[Tore Krudtaa]

I'm developing an application that the customers should be possible to use
against different databases.

Does anyone know about some good online tutorials on:

How to write portable SQL for PHP and the following databases:
MySql
Oracle
PostgreSQL
MS SQL

Example of issues that must be solved:

Example 1:

$fldList = "1,2,3,6,10";
$query = "SELECT t1.f1 FROM t1 WHERE t1.f1 IN ($fldList) ....";

Will it work in all these databases, and what if the $fldList = "", will it still work, and if it works, do the databases handle this differently?

Example 2:
I have a field in the prototype application which now is an integer
(using MySql for the prototype).

This is now storing date-time values as UNIX timestamps.
That has some limitations regarding which date-time values I can store, so
I'm considering to use the datetime type in MySql instead.
So then... will I be able to use a similar field type in the other databases?

Just some examples. Would be nice to find a few good portability documents
targeting PHP and the databases above, in order to shorten the trial and error
road.