Question

I want to know the sql statement(s) to use to delete old data and the association to the old data without deleting the more important parent table, which should live forever.

I have the following tables:

Step
  Id bigint
  OccurredOn datetime
  ScreenshotId bigint

Screenshot
  Id bigint
  Data varbinary(max)

I want to delete all Screenshots records associated with Steps where OccurredOn is more than 30 days old. The Steps would still be persisted with a null ScreenshotId.

What is the best SQL Statement(s) to do this?

Answer 1

Use:

UPDATE STEP
   SET screenshotid = NULL
 WHERE occurredon < DATEADD(dd, -30, GETDATE())

DELETE FROM SCREENSHOT
 WHERE NOT EXISTS(SELECT NULL
                    FROM STEP s
                   WHERE s.screenshotid = id)