I am building a product that can work with SQL Server, MySQL, PgSQL and Oracle. The reason was if the company who buys the software already has the infrastructu

I am building a product that can work with SQL Server, MySQL, PgSQL and Oracle. The reason was if the company who buys the software already has the infrastructure and DBAs in that database, they can leverage it. If I were making the decision now I would definitely choose just one and stick with it, because - astonishing amount of things are done differently on these four dbms (idenities/sequences and getting their last value, paging, DDL) - each of these dbms has specific features which would improve the performance or help us develop stuff but we can't use them because they require different architecture (and we want to keep it the same) Don't do software for multiple databases. It's just not worth the trouble.