SQL - condition on a timestampdiff - sql

Question

I would like to get the average time of solution time for tickets
from state 'billet ouvert' to state 'résolu'.
Table Sample
The queries I tried:
Query 1:
SELECT
title AS 'Etat', ticket_id, user_id,
AVG(TIMESTAMPDIFF(HOUR,
helpdesk_followup.date having title in ('billet ouvert'),
helpdesk_followup.date having title in ('résolu'))
) AS 'moyenne'
FROM helpdesk_followup
GROUP BY user_id;
Query 2:
SELECT
title AS 'Etat', ticket_id, user_id,
AVG(TIMESTAMPDIFF(HOUR,
helpdesk_followup.date as date1,
helpdesk_followup.date as date2)
) AS 'moyenne'
FROM helpdesk_followup
WHERE date1 having title IN 'résolu'
AND date2 having title IN 'billet ouvert'
GROUP BY user_id;
But these queries doesn't get the result I need. How can I add condition to a timestampdiff?

Answer 1

The first column is the starting event and the second column is the end event.
I have done the average in minutes. This SQL works off the title which you may wish to tweak to something more distinct
select a.title, b.title, avg(DateDiff(MINUTE, '00:00:00', b.[date] ) - DateDiff(MINUTE, '00:00:00', a.[date] ) ) from
(select *, row_number() over (order by [date]) hf from helpdesk_followup) a
join (select *, row_number() over (order by [date]) hf from helpdesk_followup) b on (a.hf=b.hf-1)
group by
a.title, b.title
I have left out the user_id from the query as I'm unsure if you wish to break it down using that field.
Hopefully its a start for you to amend into what you need
EDIT: Here is the test data I used for the query
CREATE TABLE [dbo].[helpdesk_followup](
[title] [varchar](50) NULL,
[ticket_id] [int] NULL,
[user_id] [int] NULL,
[date] [datetime] NULL
) ON [PRIMARY]
GO
SET ANSI_PADDING OFF
GO
INSERT [dbo].[helpdesk_followup] ([title], [ticket_id], [user_id], [date]) VALUES (N'billet ouvert', 133, NULL, CAST(N'2015-07-22 15:36:00.000' AS DateTime))
GO
INSERT [dbo].[helpdesk_followup] ([title], [ticket_id], [user_id], [date]) VALUES (N'résolu', 133, 19, CAST(N'2015-07-23 15:36:00.000' AS DateTime))
GO
INSERT [dbo].[helpdesk_followup] ([title], [ticket_id], [user_id], [date]) VALUES (N'billet ouvert', 134, 15, CAST(N'2015-07-23 15:36:00.000' AS DateTime))
GO
INSERT [dbo].[helpdesk_followup] ([title], [ticket_id], [user_id], [date]) VALUES (N'résolu', 134, 21, CAST(N'2015-07-27 15:36:00.000' AS DateTime))
GO