[aetherson]

That's fine for an "or" aggregation, but it's harder for an "and" aggregation, in which case I guess you'd have to say:

select category case when sum(express_delivered) = count(express_delivered) then 1 else 0 end as always_been_express_delivered from etc.

[MSM]

I think instead of trying to shoehorn the "AND" that he discusses in the article into a case statement you'd just look for each category to see if there has been a non expressed delivered package.

  SELECT 
      category, 
      ISNULL(NonExpress.NonExpress, 0) AS ever_been_non_express_delivered
  FROM @orders O
  OUTER APPLY (
     SELECT TOP 1 1 as [NonExpress]
     FROM @Orders O2
     WHERE O2.Category = O.Category
        AND express_delivered = 0
  ) NonExpress
  GROUP BY category

Edit: Changed the logic up, the original code's field was contradicting my logic.

[nickpeterson]

How about:

  CASE WHEN MIN(express_delivered) = 0 THEN 0 ELSE 1 END AS always_been_express_delivered