Find the missing number group by category - sql

Question

I want to find the missing batchNo group by each category
I try this and it work but I get all the missing number for all categories
how to group by the data ?
CREATE TABLE #tmp (BatchNo INT, Category VARCHAR(15))
INSERT INTO #tmp
SELECT 94, 'A01'
UNION ALL
SELECT 97, 'A01'
UNION ALL
SELECT 100, 'A02'
UNION ALL
SELECT 105, 'A02'
declare #valmax INT, #valmin INT, #i INT;
select #valmax=max(BatchNo) from #tmp;
select #valmin=min(BatchNo) from #tmp;
set #i=#valmin;
while (#i<#valmax) begin
if (not exists(select * from #tmp where BatchNo=#i)) begin
-- SELECT #i, Category FROM #tmp GROUP BY Category
SELECT #i
end;
set #i=#i+1
end;
the out put shold be like
95 A01
96 A01
101 A02
102 A02
103 A02
104 A02

Answer 1

You can do this by joining with a number table. This query uses thespt_valuestable and should work:
;with cte as (
select category , min(batchno) min_batch, max(batchno) max_batch
from #tmp
group by category
)
select number, category
from master..spt_values
cross join cte
where type = 'p'
and number > min_batch
and number < max_batch
group by category, number
Sample SQL Fiddle
Note that this table only has a sequence of numbers 0-2047so if yourBatchNocan be higher you need another source for the query (could be another table or a recursive cte); something like this would work:
;with
cte (category, min_batch, max_batch) as (
select category , min(batchno), max(batchno)
from #tmp
group by category
),
numbers (number, max_number) as (
select 1 as number, (select MAX(batchno) from #tmp) max_number
union all
select number + 1, max_number
from numbers
where number < max_number
)
select number, category
from numbers cross join cte
where number > min_batch
and number < max_batch
group by category, number
option (maxrecursion 0)

Answer 2

Amended my answer. Probably better than using spt_values just because there is a limit. Thanks for jpw for a better way of doing it
Declare #Start int
Declare #End int
Select #Start = Min(BatchNo), #End = Max(BatchNo) from #tmp;
with nums as (
select #Start as n
union all
select n+1
from nums
where n < #End
)
Select n, Category from nums
cross join #tmp t
where n > (select Min(BatchNo) from #tmp where Category = t.Category group by Category)
and n < (select Max(BatchNo) from #tmp where Category = t.Category group by Category)
group by category, n