Hi,

I figured out my problem... My Xpath for preceding is one node too far since
the context node is already at the myRow.  The solution should be as follows:

key = not(key = preceding::myRow/key)

Now I have another problem.  I have two keys now instead of one.  I want to
be able to filter rows based on these two keys which are unique.

For example, I have the following schema:

myRow
 Key1
 Key2
 value

Sample data:
key1   key2     value
1        a         10
1        a         20
1        b         30
1        b         40
2        a         10
2        a         20
2        b         30
2        b         40
3        a         10

I only want to see the following rows in the table:
Sample data Filtered:
key1   key2     value
1        a         10
1        b         30
2        a         10
2        b         30
3        a         10

I have tried with the following filter expression(but it doesn't work fully):

key1 = not((key1= preceding::myRow/key1) and (key2= preceding::myRow/key2))

Results...
key1   key2     value
1        a         10
1        b         30
2        a         10
2        b         30  (missing this row.. I know why.. coz 2 happens before
and b as well)
3        a         10