Krdytkyu

    SELECT DISTINCT re.*

    FROM `reports` r

    LEFT JOIN `users` u

    ON u.`id_rep` = r.`id`

    JOIN `customers` c

    ON u.`id` = r.`uid`

    WHERE r.`uid` = '1' and r.`name` LIKE 'urgent'

    ORDER BY r.date DESC

Without making any modifications prior to the WHERE clause, would it be possible to use UNION (or a better approach) after the LIKE statement in order to SELECT from a fourth table called workers and ORDER the results BY r.date DESC?

Using Union and ORDER BY:

Be explicit with results form first query:

(SELECT DISTINCT rep.name, rep.date as rdate

FROM `reports_new` rep

LEFT JOIN `repuser_new` ru

ON ru.`id_rep` = rep.`id`

JOIN `clients` c

ON c.`id` = rep.`id_client`

WHERE ru.`id_user` = '1' and rep.`name` LIKE 'urgent')



UNION

(SELECT username,rdate FROM users)





ORDER BY rdate DESC

I assumed the second table had a date column. Otherwise and explicit value could be used.

If I understand the question correctly, yes. Each of the following is OK, though not necessarily efficient:

SELECT ...

   FROM ( ( SELECT ... ) UNION ( SELECT ... ) ) AS x



SELECT ...

   FROM a

   JOIN ( ( SELECT ... ) UNION ( SELECT ... ) ) AS x ON ...



SELECT ...

   FROM a

   LEFT JOIN ( ( SELECT ... ) UNION ( SELECT ... ) ) AS x ON ...



SELECT ...

   FROM ( ( SELECT ... ) UNION ( SELECT ... ) ) AS a

   JOIN ( ( SELECT ... ) UNION ( SELECT ... ) ) AS x ON ...

etc. (I may have added more parentheses than necessary.)

More UNION tips:

• Yes, the number of columns needs to be the same.


• The default column names come from the first SELECT.


• If you have a constant string in a column of the first SELECT, that limits the length of the matching string of the other SELECTs. (Simply pad with blanks to 'fix' the problem.)


• If appropriate, use UNION ALL do avoid the de-duping phase, thereby being faster than UNION, which is the same as UNION DISTINCT.