如何在SQLite中使用序列？

I'm writing a PHP-based web application that should work with multiple database systems. The most important are MySQL and SQLite but PostgreSQL and others would also be nice. For this I try to use as portable SQL as possible. Where this isn't possible, I have defined some meta words in my queries that are handled by my DB layer and converted to platform-specific SQL commands.I'm writing a PHP-based web application that sh