来自当前和之前日期的累积列值

Question

我有一张注册表,大约有300K的记录.我需要一个SQL语句来显示该特定日期的注册总数？

select
count('x'),CONVERT(varchar(12),date_created,111)
from reg group by
cONVERT(varchar(12),date_created,111)
order by
CONVERT(varchar(12),date_created,111)

此查询的结果:

169      2011/03/24
3016     2011/03/25
2999     2011/03/26

期望的结果:

 2011/03/25  3016+169
 2011/03/26  2999+3016+169

如何才能做到这一点？

Answer 1

这里有两个版本可以做到这一点。我在一台内存不足的非常慢的计算机上测试了 6000 天的 100000 行，这表明 cte 版本比循环版本更快。如果我正确理解了问题，这里建议的其他版本（到目前为止）要慢得多。

递归 CTE（10 秒）

-- Table variable to hold count for each day
declare @DateCount table(d int, c int, rn int)
insert into @DateCount
  select 
    datediff(d, 0, date_created) as d,
    count(*) as c,
    row_number() over(order by datediff(d, 0, date_created)) as rn
  from reg
  group by datediff(d, 0, date_created)

-- Recursive cte using @DateCount to calculate the running sum
;with DateSum as
(
  select 
    d, c, rn
  from @DateCount
  where rn = 1
  union all
  select 
    dc.d, ds.c+dc.c as c, dc.rn
  from DateSum as ds
    inner join @DateCount as dc
      on ds.rn+1 = dc.rn  
)
select
  dateadd(d, d, 0) as date_created,
  c as total_num
from DateSum
option (maxrecursion 0)

循环（14 秒）

-- Table variable to hold count for each day
declare @DateCount table(d int, c int, rn int, cr int)
insert into @DateCount
  select 
    datediff(d, 0, date_created) as d,
    count(*) as c,
    row_number() over(order by datediff(d, 0, date_created)) as rn,
    0
  from reg
  group by datediff(d, 0, date_created)

declare @rn int = 1

-- Update cr with running sum
update dc set
  cr = dc.c  
from @DateCount as dc
where rn = @rn

while @@rowcount = 1
begin
  set @rn = @rn + 1

  update dc set
    cr = dc.c + (select cr from @DateCount where rn = @rn - 1)  
  from @DateCount as dc
  where rn = @rn
end

-- Get the result
select
  dateadd(d, d, 0) as date_created,
  cr as total_num
from @DateCount

编辑 1 非常快的版本

奇怪的更新

-- Table variable to hold count for each day
declare @DateCount table(d int primary key, c int, cr int)
insert into @DateCount
  select 
    datediff(d, 0, date_created) as d,
    count(*) as c,
    0
  from reg
  group by datediff(d, 0, date_created)

declare @rt int = 0
declare @anchor int

update @DateCount set
  @rt = cr = @rt + c,
  @anchor = d
option (maxdop 1)

-- Get the result
select
  dateadd(d, d, 0) as date_created,
  cr as total_num
from @DateCount                
order by d