SELF-JOIN discarding true CROSS JOIN rows - sql

Question

I have the following query;
What I get is tickets information. I use self-join to obtain the requester and the assignee in the same row:
SELECT z.id AS TICKET, z.name AS Subject, reqs.name AS Requester, techs.name AS Assignee,
e.name AS Entity,DATE_FORMAT(tt.date,'%y%-%m%-%d') AS DATE,
DATE_FORMAT(tt.date,'%T') AS HOUR,
CASE WHEN z.priority = 6 THEN 'Mayor' WHEN z.priority = 5 THEN 'Muy urgente' WHEN z.priority = 4 THEN 'Urgente'WHEN z.priority = 3 THEN 'Mediana' WHEN z.priority = 2 THEN 'Baja' WHEN z.priority =1 THEN 'Muy baja' END AS Priority,
c.name AS Category, i.name AS Department
FROM glpi_tickets_users tureq
JOIN glpi_tickets_users tutech ON tureq.tickets_id = tutech.tickets_id
JOIN glpi_users AS reqs ON tureq.users_id = reqs.id
JOIN glpi_users AS techs ON tutech.users_id = techs.id
JOIN glpi_tickets z ON z.id = tureq.tickets_id
LEFT OUTER JOIN glpi_tickettasks tt ON z.id = tt.tickets_id
LEFT JOIN glpi_itilcategories i ON z.itilcategories_id = i.id
LEFT JOIN glpi_usercategories c ON c.id = reqs.usercategories_id
INNER JOIN glpi_entities e ON z.entities_id = e.id
WHERE (tureq.id < tutech.id AND tureq.type < tutech.type) OR
(tureq.id < tutech.id AND tureq.users_id = tutech.users_id) OR
(tureq.id = tutech.id AND tureq.users_id = tutech.users_id)
The problem is that I get something like that:
1 Report jdoe jdoe Development 16-06-07 11:56:17 Mediana Software Mkt
1 Report jdoe fwilson Development 16-06-07 11:56:17 Mediana Software MKt
1 Report fwilson fwilson Development 16-06-07 11:56:17 Mediana Software Mkt
2 Task11 gwilliams gwilliams Ops 16-06-08 12:00:00 ALTA Hardware Def
3 Task12 gwilliams gwilliams Ops 16-06-08 12:01:00 ALTA Hardware Def
I don't want first and third row because is a CROSS JOIN result. Second row is OK, because jdoe is a requester and fwilson an assignee.
The problem is that sometimes requester and assignee are the same, eg: he creates a ticket for a task that himself will do. For example, 4th and 5th rows are OK.
So, how should I do to make a difference for those distinct cases, i.e.: I need to include:
tureq.id = tech.id AND req.users_id = tech.users.id
BUT NOT IF ALREADY EXISTS
tureq.id = tech.id AND req.users_id <> tech.users_id
Update
The main problem is that a user can assign to himself a ticket:
SELECT * from glpi_tickets_users WHERE type = 2 GROUP BY tickets_id HAVING COUNT(users_id)<2 limit 3;
+----+------------+----------+------+------------------+-------------------+
| id | tickets_id | users_id | type | use_notification | alternative_email |
+----+------------+----------+------+------------------+-------------------+
| 1 | 2 | 12 | 2 | 1 | NULL |
| 3 | 6 | 13 | 2 | 1 | NULL |
| 7 | 8 | 14 | 2 | 1 | NULL |
+----+------------+----------+------+------------------+-------------------+
Update 2:
It was a human mistake. The problem was really not about self-assigned tickets. Rather it was either that some tickets had not Requester or had Requester but still had not any resolver assigned.
I've found

Answer 1

As there are always the two types per ticket you are interested in, you can simply select the according records, so as to get requester and assignee per ticket.
select
t.id as ticket,
t.name as subject,
requester.name as requester,
assignee.name as assignee,
e.name as entity,
date_format(tt.date,'%y%-%m%-%d') as date,
date_format(tt.date,'%T') as hour,
case t.priority
when 6 then 'Mayor'
when 5 then 'Muy urgente'
when 4 then 'Urgente'
when 3 then 'Mediana'
when 2 then 'Baja'
when 1 then 'Muy baja'
end as priority,
uc.name as category,
ic.name as department
from glpi_tickets t
join glpi_entities e on e.id = t.entities_id
join
(
select tu.tickets_id, u.name, u.usercategories_id
from glpi_tickets_users tu
join glpi_users u on u.id = users_id
where tu.type = 1
) requester on requester.tickets_id = t.id
join
(
select tu.tickets_id, u.name
from glpi_tickets_users tu
join glpi_users u on u.id = users_id
where tu.type = 2
) assignee on assignee.tickets_id = t.id
left join glpi_itilcategories ic on ic.id = t.itilcategories_id
left join glpi_usercategories uc on uc.id = requester.usercategories_id;
left outer join glpi_tickettasks tt on tt.tickets_id = t.id
The only thing I wonder is: There can be several ticket tasks per ticket. So what do you want to do then? Have one line per ticket task in your results? This is what the query does. Only, it looks queer that your result rows don't contain any information on the tasks except for the dates, so you may have many, many lines with the same data, only with different dates. So maybe, you'd rather want the first or last date per ticket. To get the last date per ticket, you'd replace the last line in the query with:
left outer join
(
select tickets_id, max(date) as date
from glpi_tickettasks
group by tickets_id
) tt on tt.tickets_id = t.id
And you probably want to add an ORDER BY clause.

Answer 2

you need to add more qualifiers to your joins for example
JOIN glpi_tickets_users tutech ON tureq.tickets_id = tutech.tickets_id and tutech.type = 2