I have a table called TaxRates. I want to create a computed column called `EndDate`, of type `DATETIMEOFFSET NULL`.

EndDate should return the value of the StartDate column of the next record in chronological order. If there is no match it should return null.

I don't have a lot of experience with computed columns. This is what i am trying to do:

```
SELECT TOP 1 StartDate FROM TaxRates tr
WHERE tr.StartDate > StartDate
ORDER BY StartDate ASC

```

This gives a validation error.

What should I be doing here?