Remplissage des données manquantes sur la base des valeurs de fin de mois précédentes

Compte tenu des données suivantes:

create table #histories
(
    username varchar(10),
    account varchar(10),
    assigned date  
);

insert into #histories 
values 
('PHIL','ACCOUNT1','2017-01-04'),
('PETER','ACCOUNT1','2017-01-15'),
('DAVE','ACCOUNT1','2017-03-04'),
('ANDY','ACCOUNT1','2017-05-06'),
('DAVE','ACCOUNT1','2017-05-07'),
('FRED','ACCOUNT1','2017-05-08'),
('JAMES','ACCOUNT1','2017-08-05'),
('DAVE','ACCOUNT2','2017-01-02'),
('PHIL','ACCOUNT2','2017-01-18'),
('JOSH','ACCOUNT2','2017-04-08'),
('JAMES','ACCOUNT2','2017-04-09'),
('DAVE','ACCOUNT2','2017-05-06'),
('PHIL','ACCOUNT2','2017-05-07') ; 

... qui indique quand un utilisateur donné a été affecté à un compte.

Je cherche à déterminer à qui appartient un compte donné le dernier jour de chaque mois (la date attribuée est la date à laquelle le compte a transféré la propriété), avec les fins de mois manquantes renseignées (éventuellement créées à partir d'un datestableau pratique dont je dispose, avec des colonnes utiles DateKey, Dateet LastDayOfMonth, [avec l'aimable autorisation de @AaronBertrand]) 1 .

Les résultats souhaités seraient:

PETER, ACCOUNT1, 2017-01-31
PETER, ACCOUNT1, 2017-02-28
DAVE, ACCOUNT1, 2017-03-31
DAVE, ACCOUNT1, 2017-04-30
FRED, ACCOUNT1, 2017-05-31
FRED, ACCOUNT1, 2017-06-30
FRED, ACCOUNT1, 2017-07-31
JAMES, ACCOUNT1, 2017-08-31
PHIL, ACCOUNT2, 2017-01-31
PHIL, ACCOUNT2, 2017-02-28
PHIL, ACCOUNT2, 2017-03-31
JAMES, ACCOUNT2, 2017-04-30
PHIL, ACCOUNT2, 2017-05-31

Faire la première partie de cela avec une fonction de fenêtrage est trivial, c'est ajouter les lignes "manquantes" avec lesquelles je me bats.

Une approche à ce problème consiste à procéder comme suit:

1. Émuler LEADsur SQL Server 2008. Vous pouvez utiliser APPLYou une sous-requête pour cela.
2. Pour les lignes sans ligne suivante, ajoutez un mois à la date de leur compte.
3. Rejoignez une table de dimension qui contient les dates de fin de mois. Cela élimine toutes les lignes qui ne s'étendent pas sur au moins un mois et ajoute des lignes pour combler les lacunes si nécessaire.

J'ai un peu modifié vos données de test pour rendre les résultats déterministes. Ajout d'un index:

create table #histories
(
    username varchar(10),
    account varchar(10),
    assigned date  
);

insert into #histories 
values 
('PHIL','ACCOUNT1','2017-01-04'),
('PETER','ACCOUNT1','2017-01-15'),
('DAVE','ACCOUNT1','2017-03-04'),
('ANDY','ACCOUNT1','2017-05-06'),
('DAVE','ACCOUNT1','2017-05-07'),
('FRED','ACCOUNT1','2017-05-08'),
('JAMES','ACCOUNT1','2017-08-05'),
('DAVE','ACCOUNT2','2017-01-02'),
('PHIL','ACCOUNT2','2017-01-18'),
('JOSH','ACCOUNT2','2017-04-08'), -- changed this date to have deterministic results
('JAMES','ACCOUNT2','2017-04-09'),
('DAVE','ACCOUNT2','2017-05-06'),
('PHIL','ACCOUNT2','2017-05-07') ;

-- make life easy
create index gotta_go_fast ON #histories (account, assigned);

Voici le tableau des dimensions de date le plus paresseux de tous les temps:

create table #date_dim_months_only (
    month_date date,
    primary key (month_date)
);

-- put 2500 month ends into table
INSERT INTO #date_dim_months_only WITH (TABLOCK)
SELECT DATEADD(DAY, -1, DATEADD(MONTH, ROW_NUMBER() OVER (ORDER BY (SELECT NULL)), '20000101'))
FROM master..spt_values;

Pour l'étape 1, il existe de nombreuses façons d'émuler LEAD. Voici une méthode:

SELECT 
  h1.username
, h1.account
, h1.assigned
, next_date.assigned
FROM #histories h1
OUTER APPLY (
    SELECT TOP 1 h2.assigned
    FROM #histories h2
    WHERE h1.account = h2.account
    AND h1.assigned < h2.assigned
    ORDER BY h2.assigned ASC
) next_date;

Pour l'étape 2, nous devons remplacer les valeurs NULL par autre chose. Vous souhaitez inclure le dernier mois de chaque compte, il suffit donc d'ajouter un mois à la date de début:

ISNULL(next_date.assigned, DATEADD(MONTH, 1, h1.assigned))

Pour l'étape 3, nous pouvons rejoindre le tableau des dimensions de date. La colonne du tableau des dimensions est exactement la colonne dont vous avez besoin pour le jeu de résultats:

INNER JOIN #date_dim_months_only dd ON
    dd.month_date >= h1.assigned AND
    dd.month_date < ISNULL(next_date.assigned, DATEADD(MONTH, 1, h1.assigned))

Je n'ai pas aimé la requête que j'ai reçue quand j'ai tout rassemblé. Il peut y avoir des problèmes avec l'ordre de jointure lors de la combinaison de OUTER APPLYet INNER JOIN. Pour obtenir l'ordre de jointure que je voulais, je l'ai réécrit avec une sous-requête:

SELECT 
  hist.username
, hist.account
, dd.month_date 
FROM
(
    SELECT 
      h1.username
    , h1.account
    , h1.assigned
    , ISNULL(
        (SELECT TOP 1 h2.assigned
            FROM #histories h2
            WHERE h1.account = h2.account
            AND h1.assigned < h2.assigned
            ORDER BY h2.assigned ASC
        )
        , DATEADD(MONTH, 1, h1.assigned)
    ) next_assigned
    FROM #histories h1
) hist
INNER JOIN #date_dim_months_only dd ON
    dd.month_date >= hist.assigned AND
    dd.month_date < hist.next_assigned;

Je ne sais pas combien de données vous avez, donc cela pourrait ne pas avoir d'importance pour vous. Mais le plan ressemble à ce que je veux:

Les résultats correspondent aux vôtres:

╔══════════╦══════════╦════════════╗
║ username ║ account  ║ month_date ║
╠══════════╬══════════╬════════════╣
║ PETER    ║ ACCOUNT1 ║ 2017-01-31 ║
║ PETER    ║ ACCOUNT1 ║ 2017-02-28 ║
║ DAVE     ║ ACCOUNT1 ║ 2017-03-31 ║
║ DAVE     ║ ACCOUNT1 ║ 2017-04-30 ║
║ FRED     ║ ACCOUNT1 ║ 2017-05-31 ║
║ FRED     ║ ACCOUNT1 ║ 2017-06-30 ║
║ FRED     ║ ACCOUNT1 ║ 2017-07-31 ║
║ JAMES    ║ ACCOUNT1 ║ 2017-08-31 ║
║ PHIL     ║ ACCOUNT2 ║ 2017-01-31 ║
║ PHIL     ║ ACCOUNT2 ║ 2017-02-28 ║
║ PHIL     ║ ACCOUNT2 ║ 2017-03-31 ║
║ JAMES    ║ ACCOUNT2 ║ 2017-04-30 ║
║ PHIL     ║ ACCOUNT2 ║ 2017-05-31 ║
╚══════════╩══════════╩════════════╝

Ici, je n'utilise pas de table de calendrier, mais une table de nombres naturels nums.dbo.nums (j'espère que vous l'avez aussi, sinon, elle peut être facilement générée)

J'ai la réponse légèrement différente de la vôtre ('JOSH' <-> 'JAMES') car vos données contiennent ces 2 lignes:

('JOSH','ACCOUNT2','2017-04-09'),
('JAMES','ACCOUNT2','2017-04-09'),

avec le même compte et la même date et vous n'avez pas précisé lequel choisir, c'est cette situation.

declare @eom table(account varchar(10), dt date); 

with acc_mm AS
(
select account, min(assigned) as min_dt, max(assigned) as max_dt
from #histories
group by account
),

acc_mm1 AS
(
select account,
       dateadd(month, datediff(month, '19991231', min_dt), '19991231') as start_dt,
       dateadd(month, datediff(month, '19991231', max_dt), '19991231') as end_dt
from acc_mm
)

insert into @eom (account, dt) 
select account, dateadd(month, n - 1, start_dt)
from acc_mm1
      join nums.dbo.nums            
           on n - 1 <= datediff(month, start_dt, end_dt); 

select eom.dt, eom.account, a.username
from @eom eom 
     cross apply(select top 1 *
                 from #histories h 
                 where eom.account = h.account
                   and h.assigned <= eom.dt
                 order by h.assigned desc) a
order by eom.account, eom.dt;                          

Ce n'est en aucun cas une solution propre, mais elle semble fournir les résultats que vous recherchez (je suis sûr que d'autres auront des requêtes agréables, propres et entièrement optimisées pour vous).

create table #histories
(
    username varchar(10),
    account varchar(10),
    assigned date  
);

insert into #histories 
values 
('PHIL','ACCOUNT1','2017-01-04'),
('PETER','ACCOUNT1','2017-01-15'),
('DAVE','ACCOUNT1','2017-03-04'),
('ANDY','ACCOUNT1','2017-05-06'),
('DAVE','ACCOUNT1','2017-05-07'),
('FRED','ACCOUNT1','2017-05-08'),
('JAMES','ACCOUNT1','2017-08-05'),
('DAVE','ACCOUNT2','2017-01-02'),
('PHIL','ACCOUNT2','2017-01-18'),
('JOSH','ACCOUNT2','2017-04-09'),
('JAMES','ACCOUNT2','2017-04-09'),
('DAVE','ACCOUNT2','2017-05-06'),
('PHIL','ACCOUNT2','2017-05-07') ; 


IF (SELECT OBJECT_ID(N'tempdb..#IncompleteResults')) IS NOT NULL
    DROP TABLE #IncompleteResults;

DECLARE @EOMTable TABLE ( EndOfMonth DATE );
DECLARE @DateToWrite DATE = '2017-01-31';
WHILE @DateToWrite < '2017-10-31'
    BEGIN
        INSERT  INTO @EOMTable
                ( EndOfMonth )
                SELECT  @DateToWrite;

        SELECT  @DateToWrite = EOMONTH(DATEADD(MONTH, 1, @DateToWrite));
    END

    ;
WITH    cteAccountsByMonth
          AS ( SELECT   EndOfMonth ,
                        account
               FROM     @EOMTable e
                        CROSS JOIN ( SELECT DISTINCT
                                            account
                                     FROM   #histories
                                   ) AS h
             ),
        cteHistories
          AS ( SELECT   username ,
                        account ,
                        ROW_NUMBER() OVER ( PARTITION BY ( CAST(DATEPART(YEAR,
                                                              assigned) AS CHAR(4))
                                                           + ( RIGHT('00'
                                                              + CAST(DATEPART(MONTH,
                                                              assigned) AS VARCHAR(10)),
                                                              2) ) ), account ORDER BY assigned DESC ) AS rownum ,
                        CAST(DATEPART(YEAR, assigned) AS CHAR(4)) + RIGHT('00'
                                                              + CAST(DATEPART(MONTH,
                                                              assigned) AS VARCHAR(10)),
                                                              2) AS PartialDate ,
                        assigned ,
                        EOMONTH(assigned) AS EndofMonth
               FROM     #histories
             )
    SELECT  username ,
            e.EndOfMonth ,
            e.account
    INTO #IncompleteResults
    FROM    cteAccountsByMonth e
            LEFT JOIN cteHistories c ON e.EndOfMonth = c.EndofMonth
                                        AND c.account = e.account
                                        AND c.rownum = 1
SELECT  CASE WHEN username IS NULL
             THEN ( SELECT  username
                    FROM    #IncompleteResults i2
                    WHERE   username IS NOT NULL
                            AND i.account = i2.account
                            AND i2.EndOfMonth = ( SELECT    MAX(EndOfMonth)
                                                  FROM      #IncompleteResults i3
                                                  WHERE     i3.EndOfMonth < i.EndOfMonth
                                                            AND i3.account = i.account
                                                            AND i3.username IS NOT NULL
                                                )
                  )
             ELSE username
        END AS username ,
        EndOfMonth ,
        account 
FROM    #IncompleteResults i
ORDER BY account ,
        i.EndOfMonth;

J'ai utilisé la table de dimension de date d'Aaron Bertrand, comme vous le mentionnez également dans votre question (qui est une table très pratique pour de tels scénarios) et j'ai écrit le code suivant:

J'ai ajouté la EndOfMonthcolonne au #dimtableau (juste après la FirstOfMonthcolonne) en utilisant le code suivant:

 EndOfMonth as dateadd(s,-1,dateadd(mm, datediff(m,0,[date])+1,0)),

Et la solution:

if object_id('tempdb..#temp') is not null drop table #temp
create table #temp (nr int, username varchar(100), account varchar(100), eom date)

;with lastassignedpermonth as
(
    select 
           month(assigned) month
         , account
         , max(assigned) assigned
    from 
           #histories 
    group by month(assigned), account 
)
insert into #temp
select 
       distinct row_number() over (order by d.account, d.eom) nr
     , h.username
     , d.account
     , d.eom
from ( 
        select distinct month, cast(d.endofmonth as date) eom, t.account 
        from #dim d cross apply (select distinct account from #histories) t 
     ) d
            left join lastassignedpermonth l on d.month = l.month and l.assigned <= d.eom and d.account = l.account 
            left join #histories h on h.assigned = l.assigned and h.account = l.account 
where d.eom <=  dateadd(s,-1,dateadd(mm, datediff(m,0,getdate())+1,0)) -- end of current month
order by d.account, eom 

-- This could have been done in one single statement with the lead() function but that is available as of SQL Server 2012
select case when t.username is null then (select username from #temp where nr = previous_username.nr) else t.username end as username, t.account, t.eom 
from #temp as t cross apply ( 
                                select max(nr) nr 
                                from #temp as t1
                                where t1.nr < t.nr and t1.username is not null
                            ) as previous_username

/*
   Note: You get twice JAMES and JOSH for April/ACCOUNT2, because apparently they are both assigned on the same date(2017-04-09)... 
   I guess your data should be cleaned up of overlapping dates.
*/

Triangle REJOIGNEZ pour la victoire!

SELECT account,EndOfMonth,username
FROM (
    SELECT Ends.*, h.*
        ,ROW_NUMBER() OVER (PARTITION BY h.account,Ends.EndOfMonth ORDER BY h.assigned DESC) AS RowNumber
    FROM (
        SELECT [Year],[Month],MAX(DATE) AS EndOfMonth
        FROM #dim
        GROUP BY [Year],[Month]
        ) Ends
    CROSS JOIN (
        SELECT account, MAX(assigned) AS MaxAssigned
        FROM #histories
        GROUP BY account
        ) ac
    JOIN #histories h ON h.account = ac.account
        AND Year(h.assigned) = ends.[Year]
        AND Month(h.assigned) <= ends.[Month] --triangle join for the win!
        AND EndOfMonth < DATEADD(month, 1, Maxassigned)
    ) Results
WHERE RowNumber = 1
ORDER BY account,EndOfMonth;

Les résultats sont:

account     EndOfMonth  username

ACCOUNT1    2017-01-31  PETER
ACCOUNT1    2017-02-28  PETER
ACCOUNT1    2017-03-31  DAVE
ACCOUNT1    2017-04-30  DAVE
ACCOUNT1    2017-05-31  FRED
ACCOUNT1    2017-06-30  FRED
ACCOUNT1    2017-07-31  FRED
ACCOUNT1    2017-08-31  JAMES

ACCOUNT2    2017-01-31  PHIL
ACCOUNT2    2017-02-28  PHIL
ACCOUNT2    2017-03-31  PHIL
ACCOUNT2    2017-04-30  JAMES
ACCOUNT2    2017-05-31  PHIL

Plan d'exécution interactif ici.

Statistiques d'E / S et de TEMPS (tronqué toutes les valeurs nulles après les lectures logiques):

(13 row(s) affected)

Table 'Worktable'.  Scan count 3, logical reads 35.
Table 'Workfile'.   Scan count 0, logical reads  0.
Table '#dim'.       Scan count 1, logical reads  4.
Table '#histories'. Scan count 1, logical reads  1.

SQL Server Execution Times:
    CPU time = 0 ms,  elapsed time = 3 ms.

Recherchez les tables temporaires requises et testez l'instruction T-SQL que je suggère:

IF OBJECT_ID('tempdb..#histories') IS NOT NULL
    DROP TABLE #histories

CREATE TABLE #histories (
    username VARCHAR(10)
    ,account VARCHAR(10)
    ,assigned DATE
    );

INSERT INTO #histories
VALUES
('PHIL','ACCOUNT1','2017-01-04'),
('PETER','ACCOUNT1','2017-01-15'),
('DAVE','ACCOUNT1','2017-03-04'),
('ANDY','ACCOUNT1','2017-05-06'),
('DAVE','ACCOUNT1','2017-05-07'),
('FRED','ACCOUNT1','2017-05-08'),
('JAMES','ACCOUNT1','2017-08-05'),
('DAVE','ACCOUNT2','2017-01-02'),
('PHIL','ACCOUNT2','2017-01-18'),
('JOSH','ACCOUNT2','2017-04-08'),
('JAMES','ACCOUNT2','2017-04-09'),
('DAVE','ACCOUNT2','2017-05-06'),
('PHIL','ACCOUNT2','2017-05-07');

DECLARE @StartDate DATE = '20170101'
    ,@NumberOfYears INT = 2;

-- prevent set or regional settings from interfering with 
-- interpretation of dates / literals
SET DATEFIRST 7;
SET DATEFORMAT mdy;
SET LANGUAGE US_ENGLISH;

DECLARE @CutoffDate DATE = DATEADD(YEAR, @NumberOfYears, @StartDate);

-- this is just a holding table for intermediate calculations:
IF OBJECT_ID('tempdb..#dim') IS NOT NULL
    DROP TABLE #dim

CREATE TABLE #dim (
    [date] DATE PRIMARY KEY
    ,[day] AS DATEPART(DAY, [date])
    ,[month] AS DATEPART(MONTH, [date])
    ,FirstOfMonth AS CONVERT(DATE, DATEADD(MONTH, DATEDIFF(MONTH, 0, [date]), 0))
    ,[MonthName] AS DATENAME(MONTH, [date])
    ,[week] AS DATEPART(WEEK, [date])
    ,[ISOweek] AS DATEPART(ISO_WEEK, [date])
    ,[DayOfWeek] AS DATEPART(WEEKDAY, [date])
    ,[quarter] AS DATEPART(QUARTER, [date])
    ,[year] AS DATEPART(YEAR, [date])
    ,FirstOfYear AS CONVERT(DATE, DATEADD(YEAR, DATEDIFF(YEAR, 0, [date]), 0))
    ,Style112 AS CONVERT(CHAR(8), [date], 112)
    ,Style101 AS CONVERT(CHAR(10), [date], 101)
    );

-- use the catalog views to generate as many rows as we need

INSERT #dim ([date])
SELECT d
FROM (
    SELECT d = DATEADD(DAY, rn - 1, @StartDate)
    FROM (
        SELECT TOP (DATEDIFF(DAY, @StartDate, @CutoffDate)) rn = ROW_NUMBER() OVER (
                ORDER BY s1.[object_id]
                )
        FROM sys.all_objects AS s1
        CROSS JOIN sys.all_objects AS s2
        -- on my system this would support > 5 million days
        ORDER BY s1.[object_id]
        ) AS x
    ) AS y;

/* The actual SELECT statement to get the results we want! */

SET STATISTICS IO, TIME ON;

SELECT account,EndOfMonth,username
FROM (
    SELECT Ends.*, h.*
        ,ROW_NUMBER() OVER (PARTITION BY h.account,Ends.EndOfMonth ORDER BY h.assigned DESC) AS RowNumber
    FROM (
        SELECT [Year],[Month],MAX(DATE) AS EndOfMonth
        FROM #dim
        GROUP BY [Year],[Month]
        ) Ends
    CROSS JOIN (
        SELECT account, MAX(assigned) AS MaxAssigned
        FROM #histories
        GROUP BY account
        ) ac
    JOIN #histories h ON h.account = ac.account
        AND Year(h.assigned) = ends.[Year]
        AND Month(h.assigned) <= ends.[Month] --triangle join for the win!
        AND EndOfMonth < DATEADD(month, 1, Maxassigned)
    ) Results
WHERE RowNumber = 1
ORDER BY account,EndOfMonth;

SET STATISTICS IO, TIME OFF;

--IF OBJECT_ID('tempdb..#histories') IS NOT NULL DROP TABLE #histories
--IF OBJECT_ID('tempdb..#dim') IS NOT NULL DROP TABLE #dim