Help with sorting strings...

I'm trying to search a database and get a list of results of
the latest values which are of type 'STRING'. How would I do it?

For instance, I've got a dataset like the one below.

Col 1 Col 2 Col 3
---------------
Dog Blue 11a
Dog Blue 11b
Cat Blue 14
Cat Red 21a
Cat Red 21b
Fish Yellow 31
Shark Black 12a
Shark Purple 21

I only want it to return the ones with the highest 'Col 3' value, so it returns something like.

Col 1 Col 2 Col 3
----------------
Dog Blue 11b
Cat Red 21b
Fish Yellow 31
Shark Purple 21

I've tried something like this:

SELECT
table.col1,
table.col2,
table.col3
FROM
table
WHERE
1 > (
SELECT
COUNT(DISTINCT table.col3)
FROM
table tab
WHERE
tab.col3 > table.col3
)

However I get the ERR: An aggregate may not appear in the WHERE clause
unless it is in a subquery contained in a HAVING clause or select
list, and the column being aggregated is an outer reference.I don't what your backend database is but this should help.

SELECT t.col1
, t.col2
, t.col3
FROM tablex t
, (SELECT tablex.col1
, max (tablex.col3) col3
FROM tablex
group by col1) g
WHERE t.col1 = g.col1
AND t.col3 = g.col3
;

or using ANSI joins

SELECT t.col1
, t.col2
, t.col3
FROM tablex t
JOIN (SELECT tablex.col1
, max (tablex.col3) col3
FROM tablex
group by col1) g
ON t.col1 = g.col1
AND t.col3 = g.col3
;|||Thanks for your help gannet.