Get list of dates without entries in SQL Server - sql-server

Question

I am looking to find a solution to this problem. I have a table called LogEntry that stores information used by multiple offices, where they have to log any visitors that come in to their office on any given day. If no visitors come in, they are still required to log "No Visitors" for the day. How do I run a query that pulls all dates where an office failed to create even a "No Visitors" log?
I've looked at this question (and the article linked within), but even adapting that query, I'm only able to create a blank row for a date where an office is missing an entry for a date, not specify the actual office that did not create an entry. Is there a way to do what I'm trying to do?
declare #temp table (
CDate datetime,
loc_id varchar(50)
)
insert into #temp SELECT DISTINCT entryDate, locationID FROM LogEntry WHERE entryDate >= '05/01/2017' AND entryDate <= '07-31-2017'
;with d(date) as (
select cast('05/01/2017' as datetime)
union all
select date+1
from d
where date < '07/31/2017'
)
select DISTINCT t.loc_id, CONVERT(date, d.date)
FROM d LEFT OUTER JOIN #temp t ON d.date = t.CDate
GROUP BY t.loc_id, d.date
ORDER BY t.loc_id
As I said, this query returns me a list of dates in the date range, and all locations that submitted entries on that date, but I'd like to find a way to extract essentially the opposite information: if an office (specified by locationID) did not submit an entry on a given day, return only those locationIDs and the dates that they missed.
Sample data
EntryID | locationID | entryDate
=================================
1 1 07-01-2017
2 1 07-02-2017
3 2 07-02-2017
4 1 07-04-2017
Expected Result (for date range of 07-01 to 07-04)
locationID | missedEntryDate
============================
1 07-03-2017
2 07-01-2017
2 07-03-2017
2 07-04-2017

Answer 1

Your first step was good, you create a list of all dates, but you also need a list of all locations. Then you create a cross join to have all combinations and then you perform the left join to find out what is missing.
;with allDates(date) as (
select cast('05/01/2017' as datetime)
union all
select date+1
from d
where date < '07/31/2017'
), allLocations as (
SELECT DISTINCT loc_id
FROM #temp
), allCombinations as (
SELECT date, loc_id
FROM allDates
CROSS JOIN allLocations
)
SELECT AC.loc_id, AC.date
FROM allCombinations AC
LEFT JOIN #temp t
ON AC.date = t.CDate
AND AC.loc_id = t.loc_id
WHERE t.loc_id IS NULL -- didnt find a match on #temp

Answer 2

If your dataset is not too large you can try this:
select t.loc_id, CONVERT(date, d.date)
FROM d
-- Cross join dates to all available locs
CROSS JOIN (SELECT DISTINCT loc_id FROM #temp ) AS Locs
LEFT JOIN
( SELECT loc_id, t.CDate
FROM #temp
GROUP BY loc_id, d.date ) AS t ON d.date = t.CDate AND Locs.loc_id = t.loc_id
ORDER BY Locs.loc_id
This should be a bit faster:
;WITH cte AS (
SELECT a.LocID, RangeStart.CDate, ( CASE WHEN Input.LocID IS NULL THEN 1 ELSE 0 END ) AS IsMissing
FROM ( SELECT DISTINCT LocID FROM #temp ) AS a
CROSS JOIN ( SELECT CONVERT( DATETIME, '2017-05-01' ) AS CDate ) AS RangeStart
LEFT JOIN
( SELECT LocID, MIN( CDate ) AS CDate
FROM #temp
WHERE CDate = '2017-05-01'
GROUP BY LocID ) AS Input ON a.LocID = Input.LocID AND RangeStart.CDate = Input.CDate
UNION ALL
SELECT a.LocID, a.CDate + 1 AS CDate,
ISNULL( ItExists, 0 ) AS IsMissing
FROM cte AS a
OUTER APPLY( SELECT LocID, 1 AS ItExists FROM #temp AS b WHERE a.LocID = b.LocID AND a.CDate + 1 = b.CDate ) AS c
WHERE a.CDate < '2017-07-01'
)
SELECT * FROM cte OPTION( MAXRECURSION 0 )
You can also add an index:
CREATE INDEX IX_tmp_LocID_CDate ON #temp( LocID, CDate )
Sample data set for the second query:
CREATE TABLE #temp( LocID VARCHAR( 50 ), CDate DATETIME )
INSERT INTO #temp
VALUES
( '1', '2017-05-01' ), ( '1', '2017-05-02' ), ( '1', '2017-05-03' ), ( '1', '2017-05-04' ), ( '1', '2017-05-05' ),
( '2', '2017-05-01' ), ( '2', '2017-05-02' ), ( '2', '2017-05-03' ), ( '2', '2017-05-04' ), ( '2', '2017-05-05' )
;WITH d AS (
SELECT CAST( '05/01/2017' AS DATETIME ) AS date
UNION ALL
SELECT date + 2
FROM d
WHERE date < '2018-07-31'
)
INSERT INTO #temp
SELECT LocID, d.date
FROM ( SELECT DISTINCT LocID FROM #temp ) AS a
CROSS JOIN d
OPTION( MAXRECURSION 0 )