sql获取运行总计的上一行值

Question

I have a query that is already calculating a running total for new clients and clients that have left. However if there are no new clients or no clients have left when I try to plot this on a graph I get blank spaces.

How can I get the previous years figures if a year is null?

select x.Year
        , case when x.TotalClients is null then 0 else x.TotalClients end as 'TotalNewClients'
        , x.RunningTotal as 'RunningTotalNewClients'
        , case when x2.TotalClients is null then 0 else x2.TotalClients end as 'TotalLeftClients'
        , x2.RunningTotal as  'RunningTotalLeftClients'
from (
        SELECT
            st1.YearStart as 'Year',
            st1.TotalClients,
            RunningTotal = SUM(st2.TotalClients)
        FROM
            @TotalsStart AS st1
        INNER JOIN
            @TotalsStart AS st2
            ON st2.YearStart <= st1.YearStart
        GROUP BY st1.YearStart, st1.TotalClients) as x
left outer join 
        (SELECT
            st1.YearStart  as 'Year',
            st1.TotalClients,
            RunningTotal = SUM(st2.TotalClients)
        FROM
            @TotalsEnd AS st1
        INNER JOIN
            @TotalsEnd AS st2
            ON st2.YearStart <= st1.YearStart
        GROUP BY st1.YearStart, st1.TotalClients
        ) as x2 on x.Year = x2.Year
Order by x.Year

Answer 1

滞后功能（msdn.microsoft.com/en-us/library/hh231256.aspx）也许可以帮助您？

Answer 2

This was my amended code, I changed 2 lines in the select to use the lag function, I used the link in my answer to get this working.

select x.Year
        , case when x.TotalClients is null then 0 else x.TotalClients end as 'TotalNewClients'
        , x.RunningTotal 
        , case when x.RunningTotal is null then lag(x.RunningTotal,1,0) over(order by x.year) else x.RunningTotal end as  'RunningTotalNewClients'
        , case when x2.TotalClients is null then 0 else x2.TotalClients end as 'TotalLeftClients'
        , x2.RunningTotal
        , case when x2.RunningTotal is null then lag(x2.RunningTotal,1,0) over(order by x.year) else x2.RunningTotal end as  'RunningTotalLeftClients'
from (
        SELECT
            st1.YearStart as 'Year',
            st1.TotalClients,
            RunningTotal = SUM(st2.TotalClients)
        FROM
            @TotalsStart AS st1
        INNER JOIN
            @TotalsStart AS st2
            ON st2.YearStart <= st1.YearStart
        GROUP BY st1.YearStart, st1.TotalClients) as x
left outer join 
        (SELECT
            st1.YearStart  as 'Year',
            st1.TotalClients,
            RunningTotal = SUM(st2.TotalClients)
        FROM
            @TotalsEnd AS st1
        INNER JOIN
            @TotalsEnd AS st2
            ON st2.YearStart <= st1.YearStart
        GROUP BY st1.YearStart, st1.TotalClients
        ) as x2 on x.Year = x2.Year
Order by x.Year

Answer 3

Your query is way to complicated if you are using SQL Server 2012+. Just use the cumulative sum functionality:

select coalesce(x.Year, x2.year) as year,
       coalesce(x.TotalClients, 0 ) as TotalNewClients,
       x.RunningTotal as RunningTotalNewClients
       coalesce(x2.TotalClients, 0) as TotalLeftClients,
       x2.RunningTotal as RunningTotalLeftClients
from (SELECT st.YearStart as Year, st.TotalClients,
             SUM(st.TotalClients) over (order by year) as RunningTotal
      FROM @TotalsStart st
     ) x full outer join 
     (SELECT st.YearStart  as Year, st.TotalClients,
             SUM(st.TotalClients) over (order by year) as RunningTotal
      FROM @TotalsEnd AS st
    ) x2
    on x.Year = x2.Year
Order by coalesce(x.Year, x2.year);

Even in earlier versions of SQL Server, apply is a better method for getting cumulative sums than join with group by .

By the way, you should use single quotes only for string and date constants, not for column aliases. Although allowed in that context, they generally lead to confusion and hard-to-find errors in the query.