SQL over子句 - 将分区划分为编号的子分区

Question

我遇到了一个挑战,我曾经多次遇到但从未能找到有效的解决方案.想象一下,我有一张大表,其中包含有关银行账户及其从借方到贷方的可能循环移动的数据:

AccountId DebitCredit AsOfDate
--------- ----------- ----------
aaa       d           2018-11-01
aaa       d           2018-11-02
aaa       c           2018-11-03
aaa       c           2018-11-04
aaa       c           2018-11-05
bbb       d           2018-11-02
ccc       c           2018-11-01
ccc       d           2018-11-02
ccc       d           2018-11-03
ccc       c           2018-11-04
ccc       d           2018-11-05
ccc       c           2018-11-06

在上面的例子中,我想将子分区号分配给AccountId和DebitCredit的组合,其中每次DebitCredit移位时分区号都会递增.换句话说,在上面的示例中,我希望得到以下结果:

AccountId DebitCredit AsOfDate   PartNo
--------- ----------- ---------- ------
aaa       d           2018-11-01      1
aaa       d           2018-11-02      1
aaa       c           2018-11-03      2
aaa       c           2018-11-04      2
aaa       c           2018-11-05      2

bbb       d           2018-11-02      1

ccc       c           2018-11-01      1
ccc       d           2018-11-02      2
ccc       d           2018-11-03      2
ccc       c           2018-11-04      3
ccc       d           2018-11-05      4
ccc       c           2018-11-06      5

我无法真正弄清楚如何快速有效地做到这一点.该操作必须每天在具有数百万行的表上完成.

在此示例中,我们保证所有帐户都有连续的行.但是,客户当然可以在当月15日开立账户和/或在第26天关闭账户.

挑战是在MSSQL 2016服务器上解决,但是一个可以在2012年(甚至可能是2008r2)运行的解决方案会很好.

您可以想象,无法确定是否只有借记卡或信用额度,或者帐户是否每天都会循环使用.

Answer 1

你可以用递归的cte做到这一点

; with
-- the purpose of `cte` is to generate running number in the order of AsOfDate
cte as
(
    select  AccountId, DebitCredit, AsOfDate, rn = row_number() over (partition by AccountId order by AsOfDate)
    from    tbl
),
-- this is the recursive CTE
rcte as
(
    -- anchor member. Starts with `PartNo 1`
    select  AccountId, DebitCredit, AsOfDate, rn, PartNo = 1
    from    cte
    where   rn  = 1

    union all

    -- recursive member. Incrememt `PartNo` if there is a change in debitcredit
    select  c.AccountId, c.DebitCredit, c.AsOfDate, c.rn,
            PartNo = case when r.DebitCredit = c.DebitCredit then r.PartNo else r.PartNo + 1 end
    from    rcte r
            inner join cte c    on  r.AccountId = c.AccountId
                                and r.rn        = c.rn - 1
)
select  *
from    rcte
order by AccountId, AsOfDate

Answer 2

如果你有sql server 2012+,你可以使用lag()和窗口求和来得到这个:

select *,sum(PartNoAdd) over (partition by AccountId order by AsOfDate asc) as PartNo_calc
from
(
    select *,
    case when DebitCredit=lag(DebitCredit,1) over (partition by AccountId order by AsOfDate asc) then 0 else 1 end as PartNoAdd
    from t 
)t2
order by AccountId asc, AsOfDate  asc

在内部查询中,PartNoAdd检查此帐户的先前DebitCard是否相同.如果是,则返回0(我们不应该添加任何内容),否则返回1.

然后外部查询PartNoAdd将此帐户的所有内容相加.