While the 'does not exist constraint solution' can be accomplished by producing a UDF for the sub query in a constraint.

The recursive query's infinite loop can be solved by...

You are right, it does need another constraint.

Update and Delete Action only available to null valued voids.

The Existence check would only return False after the update. At the time of update the check would return true. As [1] will not have been saved the table yet.

I need to put

NOT EXISTS(SELECT * FROM [TICKETS] WHERE [VOID] = [TICKET])

Into a constraint. So that the chained tickets do not form a loop.

The tickets are unique but they may not be sequential or forever increasing. So a constraint with a sub-query is necessary, but I have no idea how to do that.

[Ticket] [Void]

[0] Null

[1] [0]

[2] [1]

Ticket [0] is replaced by Ticket [1], Ticket [1] is...