* SQLite is dynamically typed.
* The text types differ in meaning between databases (text, varchar, nvarchar, varchar2, ...). I also beleive char works in different ways in different databases, but I do not use blank padded strings so I am not sure.
* Time types and fucntions are very different.
* Oracle and PostgreSQL run at a different default isolation level than MySQL and MSSQL.
* MSSQL has read locks on rows, which can cause deadlocks which cannot happen in other databases.
* Autoincrement is not implemented in the same way in different databases.
* Text collations and text equality works differently in different datbases. (If they care about trailing blanks, case, etc and the order tuples are sorted in.)
And these are jsut the ones I recall on top of my head.
