I've got a table of transactions which are linked up in pairs based on the column 'Ref'. 'F's are the identifiers of each transaction while 'S's points to the 'F' of its matching pair. I need to select all the transactions with the larger 'Tag' for each pair, can someone point me in the right direction?

Tag Ref Type
--- --- -----
1 200 F
1 201 S
2 201 F
2 200 S
3 202 F
3 203 S
4 203 F
4 202 S
5 204 F
5 205 S
6 205 F
6 204 S

Is this what you are after?

select t.tag, t.ref, t.type
from t
join (select max(tag)as tag, ref from t
group by ref) b
on t.tag = b.tag
and t.ref = b.ref

giving you the result set

6 205 F
6 204 S
4 203 F
4 202 S
2 201 F
2 200 S

Yes it is, thanks!