SSRS compare rows by text - reporting-services

Question

I have table like this:
+---------------------------------+
| Group1 |
+-------+--------+----------------+
| Item1 | Value1 | Compare |
+-------+--------+----------------+
| Item2 | Value2 | Compare |
+-------+--------+----------------+
| Item3 | Value3 | Do not compare |
+-------+--------+----------------+
| Group2 |
+-------+--------+----------------+
| Item1 | Value1 | Compare |
+-------+--------+----------------+
| Item2 | Value2 | Compare |
+-------+--------+----------------+
| Item3 | Value3 | Do not compare |
+-------+--------+----------------+
In a table like this i can have multiple groups with multiple items. I need to compare only items, where "Compare" is written. For example, i need to change the color of Value1 in Group2, if that value is grater thant Value1 in Group1. How can i do that? If there would be only one line to compare in each group, it would be easy, but i don't know what to do when there are multiple lines.

Answer 1

So you need to compare new groups with an old group that you know the name of? This query will give you any new group and compare any items named the same where they have been flagged to be compared with the original group, Group1, and give you the old and new values:
SELECT New.GroupName AS NewGroup, New.ItemName AS NewItem,
Old.Value AS OldValue, New.Value AS NewValue
FROM MyTable New
INNER JOIN MyTable Old ON
Old.GroupName = 'Group1' AND
Old.ItemName = New.ItemName
Old.CompareField = 'Compare' AND
New.CompareField = 'Compare'