The last time I did real work with Oracle and MSSQL, I must have created something like 50 megabytes of "SQL" via stored procedures and such for them. The idea of migrating away from those databases to something with compatible syntax and such would have actually been feasible, but otherwise 100% dead on arrival.
If you could "just switch" then you probably shouldn't be using RDBMS at all.
If you could "just switch" then you probably shouldn't be using RDBMS at all.