Why should you care?

One database is cheaper to operate — if isolation is enforced correctly.

See it live — copy this example

Run in SQL Server Management Studio (SSMS) or Azure Data Studio.

USE DataVerse;
IF OBJECT_ID(N'dbo.Tenants', N'U') IS NOT NULL DROP TABLE dbo.Tenants;
CREATE TABLE dbo.Tenants (
    TenantId INT IDENTITY PRIMARY KEY,
    TenantCode VARCHAR(32) NOT NULL UNIQUE,
    Name NVARCHAR(100) NOT NULL
);
CREATE NONCLUSTERED INDEX IX_Orders_Tenant_OrderId
ON dbo.Orders (TenantId, OrderId DESC)
INCLUDE (Amount);
SELECT t.TenantCode, COUNT(o.OrderId) AS Orders, SUM(o.Amount) AS Gmv
FROM dbo.Tenants t
LEFT JOIN dbo.Orders o ON o.TenantId = t.TenantId
GROUP BY t.TenantCode;

What happened?

• Tenants registry plus TenantId on Orders (from RLS lesson) enables per-tenant metrics.
• Composite index supports tenant-scoped order lists.

Practice next

1. Create Tenants and seed two rows.
2. Ensure Orders.TenantId populated.
3. Run GMV by tenant.
4. Unique (TenantId, Email) on Customers.
5. Filter one TenantCode only.

Remember

TenantId everywhere shared. Index (TenantId, …) for tenant queries. RLS enforces isolation.

B2B SaaS on DataVerse

Each shop is a tenant sharing one database.

Outcome: Ops scales one platform; RLS keeps shops apart.