Check database tables and fields exist and create if missing

We require a web based database compare and merge tool suitable for SQL server and Access databases which will use compare a target database against a known? master looking for changes. We have no end of issues with keeping different databases in sync. This will often mean more than a simple compare to solve schema mismatch issues. Often it will require manual creation of tables, fields or even data type changes to the target database. This is a time consuming issue that we frequently come across. We would like to have an automated method of comparing a database to a known master? database and ensuring the database schema matches the master database. The master database may be MS Access but is more likely to be SQL Server. The target database will be either MS Access or SQL Server. To ensure compatability, the create and alter tables generated by the application must cater for the differences. This will include memo type fields in Access mapping nvarchar(max) in sql, indentity fields in SQL mapping to autonumber in Access to name a few. The application will be web based and portable so we can copy it as required to different servers. The user will enter a connection string to the master database and the target database. The target database will be compared to the master database and a list of differences displayed. The user can then accept the recommended changes the target database will be modified to comply with the master database. At no time will the target database drop tables as all changes will be either create or alter tables.