Pivoting Row Counts into Ratios Column? (in MS-SQL)

Question

I've got the following query:

select a.IsCancelled, count(*) from tblTask a
    inner join tblTicket t on a.TicketID = t.TID
    group by a.IsCancelled

Which gives me something like:

IsCancelled      Count
0                7851
1                11235

Say I wanted to add another column with the percentages relative to each row, I should get the following:

IsCancelled      Count     Ratio
0                7851      0.41135
1                11235     0.58865

This is called a Pivot correct? How would I accomplish this calculation? What do I add to my query above to make this happen? Thanks ;)

IMPLEMENTATION

I ended up modifying diaho's answer a bit as follows:

declare @tbl table (IsCancelled bit, [Count] int)
insert into @tbl
    select a.IsCancelled, count(*) [Count] from tblTask a
        inner join tblTicket t on a.TicketID = t.TID
        group by a.IsCancelled
select IsCancelled, [Count], round(cast([Count] as float)/(select sum([Count])
    from @tbl),5) [Ratio] from @tbl

Answer 1

You'll have to use a subquery. The query below should work in sqlserver and mysql, but I'm not sure it will work in ever rdbms.

select a.IsCancelled, count(*), count(*)/(select count(*) from tblTask) 
from tblTask a
inner join tblTicket t on a.TicketID = t.TID
group by a.IsCancelled

An alternate way...

select a.IsCancelled, count(*), count(*)/totalcount
from tblTask a,
tblTicket t,
(select IsCancelled, count(*) as totalcount from tblTask) as tablecount, 
where a.TicketID = t.TID
group by a.IsCancelled

The key here is to do this in one query or transaction or your count could change from one query to the next.

Answer 2

try the following

DECLARE @Total INT

SELECT @Total = select count(1) from tblTask

select a.IsCancelled, count(1), count(1)/@Total
from tblTask a
inner join tblTicket t on a.TicketID = t.TID
group by a.IsCancelled

Answer 3

If you are using SQL Server 2005 or later:

SELECT
  a.IsCancelled,
  Count = COUNT(*),
  Ratio = COUNT(*) * 1.0 / SUM(COUNT(*)) OVER ()
FROM tblTask a
  INNER JOIN tblTicket t ON a.TicketID = t.TID
GROUP BY a.IsCancelled

References:

• Aggregate Functions (Transact-SQL)

• OVER Clause (Transact-SQL)