SQL Server database schema (and likely, some data changes) - how to auto-distribute over many database instances Our development involves a SQL Server database (also might be Oracle or Postgres later) and we would sometimes make database schema changes or some other interventions in database.

What solutions exist to create a "patch" or "script" to distribute these changes on other installations of same database (we do not have direct access to these)? It needs to alter database schema and execute SQL and/or other complex, pre-programmed database data alterations as defined by person who initializes/designs change. On other instances, a system admin should be able just run some program/press button, so these changes would be applied automatically. 

In addition, it is  plus if such solution can take database snapshot and derive "difference" on contents of particular table that would be then distributed. 

The solution can be commercial.

Thanks in advance!
Rather than trying Opensource or free tools, I would highly recommend using Redgate tools for schema comparison. (note: I am not working for or affiliated to Redgate, but have and is using the schema and data compare and trust me they are life saving !)

For sql server : SQL Compare.

Useful resource for automating using Powershell or command line.

for Oracle : Schema Compare for Oracle

Note: Just to mention, there is Data compare to sync data as well.