Under the hood: Database Catalog

Under the hood: Database Catalog

  
technically: how does outsystems reference a foreign key from a different database?
We don't.

We simply fill in the value, but the integrity is not maintained. SQL Server doesn't support having foreign keys between databases. In order to maintain a consistent behavior, while it would technically be possible to have foreign keys between tables in different schemas in Oracle, we don't add those foreign keys. In MySQL I don't believe we support the multiple database catalog feature.
Ricardo Silva wrote:
We don't.

We simply fill in the value, but the integrity is not maintained. SQL Server doesn't support having foreign keys between databases. 
 
Yes thats what I am thinking, what did outsystems do to maintain data integrity and you just answered that question, outsystem does not maintain data integrity! So the safest way to maintain data integrity when using database catalog is to use Oracle database! (no other option is safe!)

Please note that we don't add the foreign keys between different schemas even in Oracle, so as to maintain the same semantics as the multiple database catalog feature in SQL Server.

This means that you won't get referential integrity even if using Oracle, so it makes no difference whether you use Oracle or SQL Server, at this time.