How to calculate with date ranges

Question

Ok this coding piece - the TAT - may be simple for you but I am beating my head over this.

This returns the # of toys for each girl

Select Toys,
Count(Girls),
TAT
from Table1 (nolock)

ie

Girl       Toys           TAT
_____      ______         ___________

Kelly       1              0-5
Michelle    1              16-30
Grace       1              31+
Katy        1              6-10
Kelly       1              16-30

This returns the # of Toys in each age range

Select TAT,
Count(TAT)
from Table1 (nolock)

ie

TAT          ??????
_____        ___________
0-5             1
6-10            0
11-15           1
16-30           2
31+             1

The next step I need do is to divide 1 (Kelly for 16-30) by # of Toys in age range it was put in (2 for 16-30) :

1  / 2  = 50.00%

How do I do that? The column with the ???? is where I am stuck at.

Thank you! Holly

Answer 1

You sound really confused - out of the goodness of my heart, I took a stab at this. If this is not correct, you need to post more information on what exactly you need.

a. Your example queries are not correct (they will error due to missing GROUP BY )

b. Your sample data is incomplete. In the first step, your data seems to indicate you want to group by Girl and TAT, but you explicitly say your query is counting toys per girl - not toys per Girl/TAT pair. Which is right?

"show the % of each toy(s) in each date range". This is not so simple when the sample data is incomplete

;WITH GirlTATCount AS (
  SELECT
    Girl,
    TAT,
    COUNT(*) as [ToyCount]
  FROM Table1
  GROUP BY Girl, TAT
)
, ToysInAgeRange AS (
  SELECT
    TAT,
    COUNT(*) as [ToyCount]
  FROM Table1
  GROUP BY TAT
)
SELECT
  gtc.Girl,
  gtc.TAT,
  gtc.ToyCount,
  CAST(gtc.ToyCount as float) / CAST(tar.ToyCount as float) as [%]
FROM GirlTATCount gtc
JOIN ToysInAgeRange tar
  ON tar.TAT = gtc.TAT

Answer 2

create table #table1 (Girl varchar(20), toys int, tat varchar(10))  
insert into #table1 (Girl, toys, tat)  
 values ('Kelly',1,'0-5')  
,('Michelle',1,'16-30')  
,('Grace',1,'31+')  
,('Katy',1,'6-10')  
,('Kelly',1,'16-30')  

declare @dividend numeric(5,2) = 1  
;with gtcount as (select tat, COUNT(*) ctr  
                  from #table1  
                  group by tat )  
select tat,ctr, @dividend/ctr percentage from gtcount  

Hope this helps...
Elmer