SQL find bad combination

Question

I have the following table

item_id     dep_id          value_id
67          20              3
67          20              2
68          20              8 
68          20              8
68          20              8
97          16              3

I need to make sure that the table has the same value_id for each item in each department_id. In other words I must not have an item_id with different value_id for a given department_id.

In the above example the first two rows are invalid because the item 67, in department_id 20 appears with different value_ids (3,2)

Is there a query to perform in order to catch the "anomalies"? I am using SQL Server 2005

Thanks in advance!

Answer 1

This will list you the (item_id, dep_id) pairs where there are different valud_is's.

select
  item_id,
  dep_id
from
  table
group by
  item_id,
  dep_id
having
  count(distinct value_id)>1

Answer 2

DISTINCT is usually more expensive, this might use less resources (and additionally shows two different values):

select
  item_id,
  dep_id,
  min(value_id),
  max(value_id)
from
  table
group by
  item_id,
  dep_id
having
  min(value_id) <> max(value_id)