Removing Duplicate Rows in SQL - sql

Question

I have a query that returns a list of devices that have multiple "moved" dates. I only want the oldest date entry. I used the MIN function to give me the oldest date, but I'm still getting multiple entries (I am, however, getting less than before). I tried to get a more precise JOIN, but I couldn't narrow the fields down any more.
If you'll look at the screenshot, the first three rows have the same "wonum" but three different "Moved Dates." I am thinking that if I can somehow take the oldest "Moved Date" out of those three and remove the other rows, that would give me the result I'm looking for. However, I'm not skilled enough to do that (I've only been working in SQL for a few months now). Would that work, or is there a better way to narrow down my results? I'm wondering if I need to perform some kind of sub-query to get what I need.
I've looked around but can't find anything that allows me to remove a row of data the way I'm looking to. Nor can I seem to find a reason my MIN function isn't paring down the data anymore than it is. Below is the code I'm currently using. Thanks for any help that can be given.
SELECT wo.wonum, wo.location, wo.statusdate, wo.status, l.subcontractor,
wo.description, MIN(ast.datemoved) AS 'Moved Date'
FROM workorder wo
JOIN locations l ON wo.location = l.location
JOIN asset a ON wo.location = a.location
-- AND wo.assetnum = a.assetnum
JOIN assettrans ast ON a.assetnum = ast.assetnum
-- AND a.assetid = ast.assetid
WHERE wo.description LIKE '%deteriorating%'
AND wo.status != 'close'
GROUP BY wo.wonum, wo.location, wo.statusdate,
wo.status, l.subcontractor, wo.description
ORDER BY wo.wonum;
DBV SQL Query Result
Update: Table Data

Answer 1

You need to do the grouping in your join statement inside a subquery(not tested, but you'll get the idea):
Replace
JOIN assettrans ast ON a.assetnum = ast.assetnum
With
inner join
(
select ast.assetnum,MIN(ast.datemoved) AS 'Moved Date'
from assettrans ast
group by ast.assetnum
) grouped
on a.assetnum = grouped.assetnum
So the full query looks like:
SELECT wo.wonum, wo.location, wo.statusdate, wo.status, l.subcontractor,
wo.description, grouped.MovedDate
FROM workorder wo
JOIN locations l ON wo.location = l.location
JOIN asset a ON wo.location = a.location
INNER JOIN
(
select ast.assetnum,MIN(ast.datemoved) AS MovedDate
from assettrans ast
group by ast.assetnum
) grouped
on a.assetnum = grouped.assetnum
WHERE wo.description LIKE '%deteriorating%'
AND wo.status != 'close'
ORDER BY wo.wonum;

Answer 2

Please test before using in production
--if you have id column and leave the oldest record
delete from T1 from MyTable T1, MyTable T2
where T1.dupField = T2.dupField (and add more filters if applies)
and
T1.uniqueField > T2.uniqueField
--if you want to delete the new "Moved Dates" and leave the oldest one
delete from T1 from MyTable T1, MyTable T2
where T1.dupField = T2.dupField (and add more filters if applies)
and
T1.Moved Dates > T2.Moved Dates