Sum when field does not exist - sql

Question

I have the following table:
create table #tbl
(
[type] varchar(20),
[qty] int
)
insert into #tbl values ('Type A', 10)
insert into #tbl values ('Type A', 15)
insert into #tbl values ('Type B', 5)
insert into #tbl values ('Type B', 8)
Now I want to display the total qty of each individual 'type':
select
isnull([type], 'Other') as [type],
sum(case
when [type] = 'Type A' then qty
when [type] = 'Type B' then qty
when [type] = 'Type C' then qty
else 0
end) as [total]
from #tbl
where [type] in ('Type A', 'Type B', 'Type C')
group by [type]
It correctly sums up each 'type'. Here's the result:
type total
--------------
Type A 25
Type B 13
But I want Type C to be included in the result as well (with a total qty of 0).
type total
--------------
Type A 25
Type B 13
Type C 0
How can I accomplish that?
I'm using MS SQL Server 2005.

Answer 1

The problem is that you don't have Type C in the table so there is nothing to return. One way you could this is to create a derived table with all of the values that you want include and then LEFT JOIN your table:
select d.type,
sum(coalesce(t.qty, 0)) Total
from
(
select 'Type A' type union all
select 'Type B' type union all
select 'Type C' type
) d
left join tbl t
on d.type = t.type
group by d.type;
See SQL Fiddle with Demo

Answer 2

You will need a table containing the list of types you want to report and do a left join on that. Something like the following:
create table #tbl
(
[type] varchar(20),
[qty] int
);
insert into #tbl values ('Type A', 10)
insert into #tbl values ('Type A', 15)
insert into #tbl values ('Type B', 5)
insert into #tbl values ('Type B', 8)
create table #types ( [type] varchar(20) );
insert into #types values ('Type A' );
insert into #types values ('Type B' );
insert into #types values ('Type C' );
select t.[type], [Total] = IsNull(t.[total], 0)
from ( select [type] = IsNull(t.[Type], 'Other')
, [total] = sum(tbl.[qty])
from #types t
left
join #tbl tbl ON tbl.[type] = t.type
group
by t.[type]
) as t
;
The sub-query is necessary to convert the NULL sums to zero.

Answer 3

Also you can get the result by applying both the UNPIVOT and the PIVOT operators.
SELECT type, qty
FROM(
SELECT COALESCE([Type A], 0) AS [Type A],
COALESCE([Type B], 0) AS [Type B],
COALESCE([Type C], 0) AS [Type C]
FROM (
SELECT [type], [qty]
FROM #tbl
) x
PIVOT (
SUM([qty]) FOR [type] IN([Type A], [Type B], [Type C])
) p
)x
UNPIVOT (
[qty] FOR [type] IN([Type A], [Type B], [Type C])
) u
Demo on SQLFiddle