How to generate temp table with integers 1-52 for weeks of year to join on? - sql

Question

I need to create a temporary table (I think) that contains a single WeekID field with values 1 through 52, indicating each week of the calendar year. I want to be able to left join against this table on the week number based on some data I have to indicate totals for each week of the year.
Preferably would like to do this in a single query.
What I have been using outputs the last 5 weeks in which records exist, as opposed to the actual last 5 weeks, in which totals may be 0.
Here is my errant query that gives me last 5 weeks totals where tickets actually got opened:
SET DATEFIRST 1
SELECT TOP 5 * FROM
(SELECT TOP 5
DATEPART(year, t.TicketQueuedDateTime) AS 'TicketYear',
DATEPART(week, t.TicketQueuedDateTime) AS 'TicketWeek',
COUNT(t.TicketStatus) AS 'WeekTotal'
FROM TicketTable t
GROUP BY DATEPART(year, t.TicketQueuedDateTime), DATEPART(week, t.TicketQueuedDateTime)
ORDER BY TicketYear DESC, TicketWeek DESC) val
ORDER BY val.TicketYear, val.TicketWeek
Current output:
TicketYear TicketWeek WeekTotal
2018 25 13
2018 26 10
2018 27 4
2018 29 2
2018 32 1
This works great; however, I want to show the actual totals for the actual last 5 weeks, even if there hasn't been any tickets (a "0" output should be filled in where there are "gap" weeks with no tickets as well).
Expected output (assuming for sake of this post that we're in week 33 and there have been no tickets this week:
TicketYear TicketWeek WeekTotal
2018 29 2
2018 30 0
2018 31 0
2018 32 1
2018 33 0
(note: weeks with no tickets gaps are filled with "0" value, and reflects the actual last 5 weeks including current week)
MSSQL 2016 Enterprise Edition

Answer 1

Without creating temporary table, you can simplify this query using CTE, like below.
- Use recursive CTE to generate week numbers
- Get distinct years from TicketTable
- Cross join distinct years and weeks to get all combinations
- Then left join it with TicketTable to get count for each year-week
;With WEEK_CTE as (
Select 1 as WeekNo
UNION ALL
SELECT 1 + WeekNo from WEEK_CTE
WHERE WeekNo < 52
)
Select yr.Year AS 'TicketYear'
, wk.WeekNo AS 'TicketWeek'
, COUNT(t.TicketStatus) AS 'WeekTotal'
from Week_CTE wk
cross join (select distinct year(TicketQueuedDateTime) as [Year] from TicketTable) yr
left join TicketTable t on wk.WeekNo = DATEPART(WEEK, t.TicketQueuedDateTime) and yr.Year = YEAR(t.TicketQueuedDateTime)
group by yr.Year, wk.WeekNo

Answer 2

You could generate such a table in a number of ways. If you don't already have a tally table in your database (i.e. a table with sequential integers in it), I'd suggest creating one, as their usefulness is endless. Regardless, you can create one on the fly using row_number(). Then just subtract the integer value you generated from the current date in weeks, selecting the top 52 of em. Strip out the year and week, and you my friend, have got yourself the query to populate your join table.
-- Creating a numbers table
if object_id('tempdb.dbo.#Numbers') is not null drop table #Numbers
create table #Numbers
(
num int primary key clustered
)
-- Populating it with some numbers
insert into #Numbers (num)
select row_number() over (order by (select null)) - 1
from sys.all_objects
select top 52
WeeksAgo = num,
TicketYear = year(dateadd(week, -num, getdate())),
TicketWeek = datepart(week, dateadd(week, -num, getdate()))
from #Numbers

Answer 3

I reused #Xedni's query and came up with the query below:
if object_id('tempdb.dbo.#Numbers') is not null drop table #Numbers
create table #Numbers
(
num int primary key clustered
)
-- Populating it with some numbers
insert into #Numbers (num)
select row_number() over (order by (select null)) - 1
from sys.all_objects
select TicketYear = year(dateadd(week, -num, getdate())),
TicketWeek = datepart(week, dateadd(week, -num, getdate()))
from #Numbers
SELECT TOP 5 * FROM
(SELECT TOP 5
DATEPART(year, t.TicketQueuedDateTime) AS 'TicketYear',
DATEPART(week, t.TicketQueuedDateTime) AS 'TicketWeek',
COUNT(t.TicketStatus) AS 'WeekTotal'
FROM #Numbers as n
LEFT OUTER JOIN TicketTable as t ON year(dateadd(week, -n.num, getdate())) = t.DATEPART(year, t.TicketQueuedDateTime) AND datepart(week, dateadd(week, -n.num, getdate())) = DATEPART(week, t.TicketQueuedDateTime)
GROUP BY DATEPART(year, t.TicketQueuedDateTime), DATEPART(week, t.TicketQueuedDateTime)
ORDER BY TicketYear DESC, TicketWeek DESC) val
ORDER BY val.TicketYear, val.TicketWeek
PS: I was not able to test this and if you're looking for performance, this is probably not the best query to use. But try this out, if it works for you, we can work on improving the performance.
Cheers!