Find all missing Numbers using one SQL query - sql

Question

The data looks like
[Month] [Date]
---------------
201306 1
201306 2
201306 5
201306 6
201306 7
201307 1
201307 4
201307 6
201309 1
201309 2
How to find all missing Dates by Month?
Here is the expected results
[Month] [Date]
---------------
201306 3
201306 4
201307 2
201307 3
201307 5

Answer 1

I think does it and pretty efficiently
declare #T table (yy int, dd int);
insert into #T values
(201306, 1)
, (201306, 2)
, (201306, 5)
, (201306, 6)
, (201306, 7)
, (201307, 1)
, (201307, 4)
, (201307, 6)
, (201309, 1)
, (201309, 2);
with cte as
( select yy, min(dd) + 1 as mn, max(dd) as mx
from #T
group by yy
having min(dd) + 1 < max(dd)
union all
select c.yy, c.mn + 1, c.mx
from cte c
where c.mn + 1 < c.mx
)
select yy, mn as dd
from cte
except
select yy, dd
from #T t
order by yy, mn;
yy dd
----------- -----------
201306 3
201306 4
201307 2
201307 3
201307 5

Answer 2

You would need some kind of lookup tables which could has intermediate dates and use cross join with left join to find missing dates
First thought
;with cte as (
select min(date) mdate, max(date) mxdate from table
union all
select mdate+1 as mdate, mxdate
from cte c
where c.mdate < c.mxdate
)
select distinct t.Month, c.mdate
from table t cross join (select mdate from cte) c
left join table t1 on t1.month = t.Month and t1.date = c.mdate
where t1.date is null
Second thought
;with cte as (
select month, min(date) over (partition by month) mdate, max(date) over (partition by month) mxdate
from sample t union all
select month, mdate+1 as mdate, mxdate
from cte c
where c.month = month and c.mdate < c.mxdate
)
select c.month, c.mdate
from cte c left join sample t1
on t1.month = c.Month and t1.date = c.mdate
where t1.date is null
group by c.month, c.mdate
Demo

Answer 3

Consider using a recursive query
with rndata as
(
select row_number() over (partition by mon order by d) rn, * from data
), rcte as
(
select mon, d, (select max(d) from data where data.mon = rndata.mon) max_d
from rndata where rn = 1
union all
select rcte.mon, rcte.d + 1, rcte.max_d
from rcte
where rcte.d + 1 < max_d
)
select mon, d
from rcte
where not exists (
select 1
from data
where rcte.mon = data.mon and
rcte.d = data.d
)
dbfiddle demo

Answer 4

Consider using below approach.
CREATE TABLE #Date([Month] int, [Date] int)
INSERT INTO #Date
VALUES(201306, 1)
,(201306, 2)
,(201306, 5)
,(201306, 6)
,(201306, 7)
,(201307, 1)
,(201307, 4)
,(201307, 6)
,(201309, 1)
,(201309, 2)
;WITH CTE AS
(
SELECT
*,LEAD([Date]) OVER(ORDER BY [Month],[Date]) AS NextDate
FROM #Date d
)
SELECT
d.[Month], m.Dt AS [Date]
FROM CTE d
CROSS APPLY( SELECT v.Dt
FROM
(VALUES(1),(2),(3),(4),(5),(6),(7),(8),(9),(10),(11)
,(11),(12),(13),(14),(15),(16),(17),(18),(19),(20)
,(21),(22),(23),(24),(25),(26),(27),(28),(29),(30),(31)
) AS v(Dt)
WHERE v.Dt > d.Date AND v.Dt < d.NextDate
) m
The only limitation this approach has is, it is not able to find missing days that falls before first date.

Answer 5

This is a fast but still simple solution:
1) use sys.sysobjects as tally table to gett all dates in each month.
2) calc min/max range for each month to keep only gaps inside the range.
3) join tally and range to get expected dates for each month, and left join your table to math existing dates.
4) filter in WHERE condition only missing dates
declare #T table ([month] int, [date] int);
insert into #T values
(201306, 1)
, (201306, 2)
, (201306, 5)
, (201306, 6)
, (201306, 7)
, (201307, 1)
, (201307, 4)
, (201307, 6)
, (201309, 1)
, (201309, 2);
with
n as (select top 31 ROW_NUMBER() over (order by id) n from sys.sysobjects),
r as (select [month], MIN([date]) dd1, MAX([date]) dd2 from #t group by [month])
select r.[month], n [date]
from r
join n on n between dd1 and dd2
left join #T t on n.N = t.[date] and r.[month] = t.[month]
where dd2<>dd1 and t.[date] is null
order by r.[month], n

Answer 6

You can use numbers/Tally table approach like below:
See live demo
create table sample ([Month] int, [Date] int)
insert into sample values
(201306, 1)
,(201306, 2)
,(201306, 5)
,(201306, 6)
,(201306, 7)
,(201307, 1)
,(201307, 4)
,(201307, 6)
,(201309, 1)
,(201309, 2);
; with daysinmonth as
(
select * from
(
values
(1,31),(2,28),(3,31),(4,30),(5,31),(6,30),
(7,31),(8,31),(9,30),(10,31),(11,30),(12,31)
) v(m,d)
)
select [month], dd
from sample
cross apply
(
select top
(
select d from
daysinmonth
where m=cast( right(cast([Month] as varchar(6)),2) as int)
)
row_number() over ( order by (select null)) dd
from
sys.tables t1 cross join
sys.tables t2
) c
where [date]<>dd