Silo – Different databases for each tenant. Again PHPRunner has an excellent solution for this.
Bridging – Unique schema for each tenant – for me this I can’t see any great advantages to this and quite a lot of extra required work.
Row Level Security – Tenancy managed by the database – One database additional column in tables that record the tenant and prior to showing results of query the database will filter results by tenant. Policy set up with unique user for each tenant. Postgres applicable. Still requires an additional field in all the tables but it is nice to have and can be extremely quick to implement.
Client Software – Client side implemented tenancy – PHP Runner has an option to implement Row Level Security in the design of the front end.
Some points – for postgres implementing Row Level Security on tables does not carry through to the views which is a major issue for me. There are way rounds it though. It would be great to have the database managing the row level security and if you have all your tenants in one database possibly the best way to do it is using the below.