SQL Query Monthly growth percentage increase/decrease

Hi Guys,

I have stumbled across the below query from the internet and would like to know how I can apply it to my SQL query. I am currently using SQL Server 2012.

select
    month, total,
    (total::float / lag(total) over (order by month) - 1) * 100 growth
from (
    select to_char(created_at, 'yyyy-mm') as month, count(user_id) total
    from users
    group by month
) s
order by month;

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The link to this code is http://stackoverflow.com/questions/16357876/sql-query-growth-of-users-per-month-in-percentage however it is for Postgres.

Could someone please help me translate this for MS SQL. Please note that I would need to SUM my totals for a month as an account could have multiple transactions within a single month.

Many thanks
databarracksAsked:
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databarracksAuthor Commented:
0
PortletPaulfreelancerCommented:
LEAD() & LAG() functions exist in SQL Server 2012

to_char(created_at, 'yyyy-mm') is a method of getting month and year from date information, this isn't hard in TSQL basically get the 1st of a month, it gives you the same effect.
SELECT
      format(yr_month,'yyyy-MM-dd')
    , total
    , (total * 1.0 / LAG(total) OVER (ORDER BY yrZ_month) - 1) * 100 growth
FROM (
            SELECT
                  DATEADD(dd, -(DAY(created_at) - 1), created_at) AS yr_month
                , COUNT(user_id)                                  AS total
            FROM users
            GROUP BY
                  yr_month
      ) s
ORDER BY
      yr_month;

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I'm not certain that minus one belongs here, and it may be necessary to multiply that lag() value by 1.0 to get a fractional result.
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Vitor MontalvãoMSSQL Senior EngineerCommented:
Are you working with SQL Server sysusers view? Because if you do, won't work. That view don't returns deleted users.
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databarracksAuthor Commented:
Hi Guys,

PortletPaul your query seems to be working correctly:) However I am interested to know I bit more about "multiply that lag() value by 1.0" and why you are suggesting that this may be a problem?

Other than that I think we are onto a winner.
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PortletPaulfreelancerCommented:
I didn't do any testing I was just "translating" using "the little grey cells"

re:"multiply that lag() value by 1.0"
Normally I multiply the divisor by 1.0  e.g. ([someintvalue] / [someotherinteger] * 1.0) as something
So I wasn't sure if integer math would take over if that wasn't done. If you are getting good results that's fine.

I'm still not sure why that minus one exists though.
0
databarracksAuthor Commented:
Ok great thanks for your help PortletPaul I am happy with the results
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databarracksAuthor Commented:
PortletPaul is always on the ball :)
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PortletPaulfreelancerCommented:
thanks, is that a jingle?
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