I have two objects within a SQl Server 2008 R2 database, which I am trying to join together with a left join but I am unable to get the left join to return all records from the table.
The vw_academicweeks, is a view that contains for each academic year a week number, and the first day and last day of the week and contains 52 records for each academic year.
tt_activityoccurrence is a table which contains occurrences of lessons within a year, lessons will not occur in all 52 weeks of the year.
With my query I am trying to return all instances from the vw_academicweeks view to return the following information
+------------+------------+------------+------------+---------+
| ActivityID | WeekStart | StartTime | EndTime | week_no |
+------------+------------+------------+------------+---------+
| 59936 | 04/09/2017 | 05/09/2017 | 05/09/2017 | 6 |
| 59936 | 11/09/2017 | 12/09/2017 | 12/09/2017 | 7 |
| 59936 | 18/09/2017 | 19/09/2017 | 19/09/2017 | 8 |
| 59936 | 25/09/2017 | 26/09/2017 | 26/09/2017 | 9 |
| 59936 | 02/10/2017 | 03/10/2017 | 03/10/2017 | 10 |
| 59936 | 09/10/2017 | 10/10/2017 | 10/10/2017 | 11 |
| 59936 | 16/10/2017 | 17/10/2017 | 17/10/2017 | 12 |
| 59936 | Null | Null | Null | 13 |
| 59936 | 30/10/2017 | 31/10/2017 | 31/10/2017 | 14 |
| 59936 | 06/11/2017 | 07/11/2017 | 07/11/2017 | 15 |
| 59936 | 13/11/2017 | 14/11/2017 | 14/11/2017 | 16 |
| 59936 | 20/11/2017 | 21/11/2017 | 21/11/2017 | 17 |
| 59936 | 27/11/2017 | 28/11/2017 | 28/11/2017 | 18 |
| 59936 | 04/12/2017 | 05/12/2017 | 05/12/2017 | 19 |
| 59936 | 11/12/2017 | 12/12/2017 | 12/12/2017 | 20 |
| 59936 | 18/12/2017 | 19/12/2017 | 19/12/2017 | 21 |
| 59936 | Null | Null | Null | 22 |
| 59936 | Null | Null | Null | 23 |
+------------+------------+------------+------------+---------+
With the left join I can return all values except the nulls, so that the week_no column is missing rows, 13,22 and 23. I have also tried this with an outer join but receive the same information.
I feel I am missing something obvious but it is escaping me at the moment.
select
ttao.ActivityID
,dateadd(dd,datediff(dd,0,DATEADD(dd, -(DATEPART(dw, ttao.StartTime)-1), ttao.StartTime)),0) WeekStart
,ttao.StartTime
,ttao.EndTime
,aw.week_no
from
vw_AcademicWeeks AW
left join TT_ActivityOccurrence TTAO on
(dateadd(dd,datediff(dd,0,DATEADD(dd, -(DATEPART(dw, ttao.StartTime)-1), ttao.StartTime)),0))=aw.ay_start
where
ay_code='1718' and
TTAO.ActivityID='59936'
order by aw.week_no asc
Your where clause makes it an inner join by eliminating rows outside of the scope of your join. You need to move this logic up to your join statement. Note, I didn't validate your join condiditon (the dateadd...datediff logic)
select
ttao.ActivityID
,dateadd(dd,datediff(dd,0,DATEADD(dd, -(DATEPART(dw, ttao.StartTime)-1), ttao.StartTime)),0) WeekStart
,ttao.StartTime
,ttao.EndTime
,aw.week_no
from
vw_AcademicWeeks AW
left join TT_ActivityOccurrence TTAO on
(dateadd(dd,datediff(dd,0,DATEADD(dd, -(DATEPART(dw, ttao.StartTime)-1), ttao.StartTime)),0)) = aw.ay_start
and ay_code='1718'
and TTAO.ActivityID='59936'
order by aw.week_no asc
Collected from the Internet
Please contact [email protected] to delete if infringement.
Comments