Question

I am developing multitenant SaaS based application and going with Shared Database for storing all the tenant records with help of TenantId column.

Now the problem is i have some list of lookup records that needs to be shared for all the tenants. For example list of games.

GamesTable

Id
GameName

Also have another table used for storing only tenant specific records

TenantGames

Id
TenantId
GameName  

The basic need is i want to use both table data and get the necessary details (Game_Name) while joining with another transaction table like UserGames. How can i achive this with this design? Here Game_Name can be either referred from Games Shared table or TenantSpecificGames table

Is there any other DB design which allows me to do mix both common master data and tenant master data with JOIN?

Basic requirement is keep common data and allow customization for the tenants if they want to add any new items.

Answer 1

This is the design I would then use.

Games

Id
GameName
IsTenantSpecific
SomeGameSpecificColumn

TenantGames

GameId
TenantId
SomeTenantSpecificColumn
AnotherTenantSpecificColumn

Then you can query that table in a Join with:

...
FROM
    Games
    INNER JOIN UserGames ON
        UserGames.GameId = Games.Id
    LEFT JOIN TenantGames ON
        TenantGames.GameId = Games.Id
WHERE
    TenantGames.TenantId = @tenantId OR
    (
        TenantGames.TenantId IS NULL AND
        IsTenantSpecific = 0
    )

Game specific fields can be put in the Games table. Tenant specific fields can be added to the TenantGames table, and those fields will be NULL if it is not a tenant specific customization.