Re: sum divided by count ends in zero
| От | naptrel |
|---|---|
| Тема | Re: sum divided by count ends in zero |
| Дата | |
| Msg-id | FDA6282B-E532-455F-8492-45A889F8D2F3@yahoo.co.uk обсуждение исходный текст |
| Ответ на | sum divided by count ends in zero ("Dara Olson" <dolson@glifwc.org>) |
| Список | pgsql-novice |
Hi Dara,
I suspect that the problem is that the division is acting on two integers, and doing integer division.
If you have two integers, a=3 and b=10, then:
a+b = 13
a*b = 30
b-a = 7
but:
b/a = 3 because 3 will fit 3 times into 10, with 1 remaining (i.e. b % a = 1)
a/b = 0 because the result is also an integer, and 10 will not go into 3 (note: a %b = 3)
You need to 'cast' the variables a and b to floating point values so that the division produces a floating point result
E.g.:
a::float / b::float = 0.3
Nathaniel
On 24 Nov 2009, at 22:32, Dara Olson wrote:
Greetings.I am having a problem dividing a sum by a count and end up with zero, however I am able to multiply, subtract and add.Here are samples of the two views:View that groups individuals into specific groups by numbers:SELECTSUM(CASE when indiv_total_lbs <= 50 then 1 else 0 end) as "0_50",SUM(CASE when indiv_total_lbs <= 100 AND indiv_total_lbs > 50 then 1 else 0 end) as "51_100", etc.FROM wr_harvest.sh_sum_by_harvestorView that gathers overall stats:SELECTAVG (indiv_total_trips) AS ave_no_trips, etc.COUNT(DISTINCT x) AS no_harvestors, etc.FROM wr_harvest.sh_sum_by_harvestorI want to find the percent of individuals in each catagory from the first view.SELECT
a."0_50"/b.no_harvestors *100 AS "0_50percent",
a."51_100"/b.no_harvestors *100 AS "51_100percent", etc
FROM wr_harvest.sh_distribution_stats_no as a, wr_harvest.sh_harvestor_stats as bI am able to add, subtract and mulitply the values with the correct outcomes, but every time I try to divide the two numbers I end in zero.What am I doing wrong? Any help would be greatly appreciated.Miigwech in advance!Dara
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