Selecting multiple tables with matching columns but only displaying unique results - mysql

Question

Here is my existing SQL query
SELECT DISTINCT
par.WorkOrder,
l.Address,
l.Subdivision,
eml.MailDate,
lp.WorkDate
FROM
parsed AS par
LEFT JOIN emails AS eml ON eml.EmailID = par.OriginID
LEFT JOIN list AS l ON par.WorkOrder = l.WorkOrder
LEFT JOIN locateparsed AS lp ON par.WorkOrder = lp.WorkOrder
WHERE
par.Status != 0
AND l.Completed = 0
AND (lp.WorkDate IS NOT NULL OR eml.MailDate IS NOT NULL)
GROUP BY
par.WorkOrder
Right now it will only select WorkOrder matches from the parsed table. How can I also have it select WorkOrder from the locateparsed table and combine them? The best way to describe this would be something like
SELECT DISTINCT par.WorkOrder OR lp.WorkOrder FROM....
UPDATE:
Here is the completed query I am using. I just need to sort out an issue with dates now of results that come up uncompleted that were mistakenly entered.
SELECT
temp.WorkOrder,
l.Address,
l.Subdivision,
eml.MailDate,
temp.WorkDate
FROM (
(SELECT par.WorkOrder, lp.WorkDate, par.OriginID, par.Status
FROM parsed AS par
LEFT JOIN locateparsed AS lp ON par.WorkOrder = lp.WorkOrder)
UNION ALL
(SELECT lp.WorkOrder, lp.WorkDate, par.OriginID, '1' AS Status
FROM parsed AS par
RIGHT JOIN locateparsed AS lp ON par.WorkOrder = lp.WorkOrder
WHERE par.WorkOrder IS NULL)
) AS temp
LEFT JOIN emails AS eml ON eml.EmailID = temp.OriginID
LEFT JOIN list AS l ON temp.WorkOrder = l.WorkOrder
WHERE
(temp.Status != 0 OR eml.Parsed IS NULL)
AND l.Completed = 0
AND (temp.WorkDate IS NOT NULL OR eml.MailDate IS NOT NULL)
GROUP BY
temp.WorkOrder

Answer 1

SELECT DISTINCT par.WorkOrder and GROUP BY par.WorkOrder will accomplish the same thing, so you don't need to use both.
As Yuri suggested, use a full outer join:
SELECT
temp.WorkOrder,
l.Address,
l.Subdivision,
eml.MailDate,
temp.WorkDate
FROM (
(SELECT par.WorkOrder, lp.WorkDate, par.OriginID, par.Status
FROM parsed AS par
LEFT JOIN locateparsed AS lp ON par.WorkOrder = lp.WorkOrder)
UNION ALL
(SELECT lp.WorkOrder, lp.WorkDate, par.OriginID, '1' AS Status
FROM parsed AS par
RIGHT JOIN locateparsed AS lp ON par.WorkOrder = lp.WorkOrder
WHERE par.WorkOrder IS NULL)
) AS temp
LEFT JOIN emails AS eml ON eml.EmailID = temp.OriginID
LEFT JOIN list AS l ON temp.WorkOrder = l.WorkOrder
WHERE
temp.Status != 0
AND l.Completed = 0
AND (temp.WorkDate IS NOT NULL OR eml.MailDate IS NOT NULL)
GROUP BY
temp.WorkOrder
Note: In order to include the results from locateparsed, I added '1' AS Status, otherwise the WHERE condition would exclude all rows from locateparsed without a matching WorkOrder in parsed.