Why should you care?

Healthcare and finance need “what did this customer record look like last Tuesday?”

See it live — copy this example

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

USE DataVerse;
IF OBJECT_ID(N'dbo.CustomersHistory', N'U') IS NOT NULL
    ALTER TABLE dbo.Customers SET (SYSTEM_VERSIONING = OFF);
IF COL_LENGTH('dbo.Customers', 'ValidFrom') IS NULL
ALTER TABLE dbo.Customers ADD
    ValidFrom DATETIME2 GENERATED ALWAYS AS ROW START HIDDEN NOT NULL CONSTRAINT DF_Cust_ValidFrom DEFAULT SYSUTCDATETIME(),
    ValidTo   DATETIME2 GENERATED ALWAYS AS ROW END HIDDEN NOT NULL CONSTRAINT DF_Cust_ValidTo DEFAULT CONVERT(DATETIME2, '9999-12-31 23:59:59.9999999'),
    PERIOD FOR SYSTEM_TIME (ValidFrom, ValidTo);
ALTER TABLE dbo.Customers SET (SYSTEM_VERSIONING = ON (HISTORY_TABLE = dbo.CustomersHistory));
SELECT * FROM dbo.Customers FOR SYSTEM_TIME AS OF '2026-07-01';

What happened?

• Period columns mark row validity.
• SYSTEM_VERSIONING writes old versions to CustomersHistory.
• FOR SYSTEM_TIME AS OF returns the past picture.

Practice next

1. Enable system versioning on Customers carefully in lab.
2. UPDATE a name and query history.
3. Run FOR SYSTEM_TIME AS OF a timestamp.
4. FOR SYSTEM_TIME BETWEEN @a AND @b.
5. Select ValidFrom, ValidTo explicitly.

Remember

Temporal = automatic row history. Query with FOR SYSTEM_TIME. History table grows — manage it.

Patient address history

Hospital module versions demographics in DataVerse.

Outcome: Auditors reconstruct prior addresses on demand.