Sql-server – Extrapolate values and sum

sql server

I have data in the form:

|Date      |Overdrawn|
|20/09/2018|1        |
|21/09/2018|1        |
|24/09/2018|0        |
|25/09/2018|1        |
|26/09/2018|1        |

I need to sum the number of overdrawn days with the following rule:

Missing dates (weekends) should be treated the same as the last date available.

i.e. If overdrawn on Friday, Saturday and Sunday should be counted as 2 days overdrawn. If Friday is not overdrawn, Saturday and Sunday should also be treated as not overdrawn.

In the example above date 20, 21, 22, 23, 25, 26 should be treated as overdrawn and the sum should return 6.

Can someone explain how to extrapolate the overdrawn value for the missing dates before summing?

Thanks

Best Answer

Try this one:

create table #test (
    date date,
    overdrawn tinyint
)

insert into #test values
    ('2018-09-20', 1),
    ('2018-09-21', 1),
    ('2018-09-24', 0),
    ('2018-09-25', 1),
    ('2018-09-26', 1)

select sum(
        case datepart(dw, date)
            when 6 then overdrawn * 3 --Friday
            else overdrawn
        end
    )
from #test

This solution is based off the fact that the overdrawn field can either be 0 or 1 only. You'll have to include additional conditions if that's not the case.

Related Solutions

Sql-server – can I convert an integer to base-2 without a function

Unless I'm completely misunderstanding your question, then the below T-SQL should do it (please let me know if this isn't what you're looking for). It utilizes bitwise operators to pull out the bit masks for the days:

-- <TEST DATA>
create table DayTable
(
    id int identity(1, 1) not null,
    DayMask tinyint not null
)
go

insert into DayTable
values
(
    62
),
(
    12
)
-- </TEST DATA>

select
        case 
            when DayMask & 1 > 0
                then 1
            else 0
        end
    as Sunday,
        case 
            when DayMask & 2 > 0
                then 1
            else 0
        end
    as Monday,
        case 
            when DayMask & 4 > 0
                then 1
            else 0
        end
    as Tuesday,
        case 
            when DayMask & 8 > 0
                then 1
            else 0
        end
    as Wednesday,
        case 
            when DayMask & 16 > 0
                then 1
            else 0
        end
    as Thursday,
        case 
            when DayMask & 32 > 0
                then 1
            else 0
        end
    as Friday,
        case 
            when DayMask & 64 > 0
                then 1
            else 0
        end
    as Saturday
from DayTable

Sql-server – Getting Unavailable dates for renting a product that has stocks

I would use a Calendar table. This table simply has a list of dates for several decades.

CREATE TABLE [dbo].[Calendar](
    [dt] [date] NOT NULL,
 CONSTRAINT [PK_Calendar] PRIMARY KEY CLUSTERED 
(
    [dt] ASC
))

In my system it has few extra columns, such as [IsLastDayOfMonth], [IsLastDayOfQuarter], which are useful in some reports, but in your case you need just the date column. There are many ways to populate such table.

For example, 100K rows (~270 years) from 1900-01-01:

INSERT INTO dbo.Calendar (dt)
SELECT TOP (100000) 
    DATEADD(day, ROW_NUMBER() OVER (ORDER BY s1.[object_id])-1, '19000101') AS dt
FROM sys.all_objects AS s1 CROSS JOIN sys.all_objects AS s2
OPTION (MAXDOP 1);

Sample data

DECLARE @Stocks TABLE (
    StockId int
    , ProductId int
    , AvailableFromDate date);

INSERT INTO @Stocks(StockId, ProductId, AvailableFromDate) VALUES
(1, 1, '2016-01-01'),
(2, 1, '2016-01-01');

DECLARE @RentStockOrders TABLE (
    RentStockOrderId int
    , StockId int
    , BeginRentDate date
    , EndRentDate date);

INSERT INTO @RentStockOrders (RentStockOrderId, StockId, BeginRentDate, EndRentDate) VALUES
(1, 1, '2016-01-15', '2016-02-14'),
(2, 2, '2016-01-30', '2016-02-20'),
(3, 2, '2016-02-26', '2016-03-07'),
(4, 1, '2016-02-29', '2016-03-14');

Parameters

DECLARE @ParamProductID int = 1;
DECLARE @ParamDays int = 14;
DECLARE @ParamStartDate date = '2015-12-01';
DECLARE @ParamEndDate date = '2017-01-01';
-- these dates define some reasonable limit

First variant

It turns out that window functions accept only literal constant as a size of a window, not a variable. Alas. Still, I'll show this query, because it illustrates the approach and shows how simple it would be if SQL Server supported variables as the size of the window. It also gives the correct answer that we can use to verify the second variant.

WITH
CTE_AllDays
-- list all days and stock IDs between @ParamStartDate and @ParamEndDate
-- for each day and stock indicate whether it is available based on AvailableFromDate
AS
(
    SELECT
        S.StockId
        ,dbo.Calendar.dt
        ,CASE WHEN dbo.Calendar.dt >= S.AvailableFromDate 
            THEN 1 ELSE 0 END AS AvailableStockDay
        -- 1 - available
        -- 0 - not available
    FROM
        @Stocks AS S
        INNER JOIN dbo.Calendar ON
            dbo.Calendar.dt >= @ParamStartDate
            AND dbo.Calendar.dt <= @ParamEndDate
    WHERE
        S.ProductId = @ParamProductID
)
,CTE_BookedDays
-- list all booked (unavailable) days for each stock ID
AS
(
    SELECT
        S.StockId
        ,CA.dt
        ,0 AS AvailableStockDay
        -- 0 - not available
    FROM
        @RentStockOrders AS R
        INNER JOIN @Stocks AS S ON S.StockId = R.StockId
        CROSS APPLY
        (
            SELECT dbo.Calendar.dt
            FROM dbo.Calendar
            WHERE
                dbo.Calendar.dt >= @ParamStartDate
                AND dbo.Calendar.dt <= @ParamEndDate
                AND dbo.Calendar.dt >= R.BeginRentDate
                AND dbo.Calendar.dt <= R.EndRentDate
        ) AS CA
    WHERE
        S.ProductId = @ParamProductID
)
,CTE_Daily
-- combine individual availability flags
-- first: multiply to get the final availability for a stock ID and day
-- second: group further by day and SUM flags
AS
(
    SELECT
        CTE_AllDays.dt
        ,CASE WHEN 
            SUM(
            CTE_AllDays.AvailableStockDay * ISNULL(CTE_BookedDays.AvailableStockDay, 1)
            ) = 0 
        THEN 0 ELSE 1 END AS AvailableDay
        -- day is available, if any stock is available
        -- SUM=0 - not available
        -- SUM>0 - available
    FROM
        CTE_AllDays
        LEFT JOIN CTE_BookedDays ON
            CTE_BookedDays.StockId = CTE_AllDays.StockId AND
            CTE_BookedDays.dt = CTE_AllDays.dt
    GROUP BY
        CTE_AllDays.dt
)
,CTE_Sum
-- rolling sum of flags with 14 days window
AS
(
    SELECT
        dt
        ,SUM(CTE_Daily.AvailableDay) OVER (ORDER BY CTE_Daily.dt
            ROWS BETWEEN CURRENT ROW AND 13 FOLLOWING) AS AvailableConsecutive
    -- we can't put @ParamDays here instead of constant
    FROM CTE_Daily
)
-- If a rolling sum =  14, 
-- it means that all 14 consecutive days are available

-- If a rolling sum <> 14, 
-- it means that at least one of the 14 consecutive days is not available
SELECT dt
FROM CTE_Sum
WHERE AvailableConsecutive <> 14
-- we can put @ParamDays here instead of 14, but not above
ORDER BY dt;

Result

Note, I started the range of dates from 2015-12-01, before the general availability.

+------------+
|     dt     |
+------------+
| 2015-12-01 |
| 2015-12-02 |
| 2015-12-03 |
| 2015-12-04 |
| 2015-12-05 |
| 2015-12-06 |
| 2015-12-07 |
| 2015-12-08 |
| 2015-12-09 |
| 2015-12-10 |
| 2015-12-11 |
| 2015-12-12 |
| 2015-12-13 |
| 2015-12-14 |
| 2015-12-15 |
| 2015-12-16 |
| 2015-12-17 |
| 2015-12-18 |
| 2015-12-19 |
| 2015-12-20 |
| 2015-12-21 |
| 2015-12-22 |
| 2015-12-23 |
| 2015-12-24 |
| 2015-12-25 |
| 2015-12-26 |
| 2015-12-27 |
| 2015-12-28 |
| 2015-12-29 |
| 2015-12-30 |
| 2015-12-31 |
| 2016-01-17 |
| 2016-01-18 |
| 2016-01-19 |
| 2016-01-20 |
| 2016-01-21 |
| 2016-01-22 |
| 2016-01-23 |
| 2016-01-24 |
| 2016-01-25 |
| 2016-01-26 |
| 2016-01-27 |
| 2016-01-28 |
| 2016-01-29 |
| 2016-01-30 |
| 2016-01-31 |
| 2016-02-01 |
| 2016-02-02 |
| 2016-02-03 |
| 2016-02-04 |
| 2016-02-05 |
| 2016-02-06 |
| 2016-02-07 |
| 2016-02-08 |
| 2016-02-09 |
| 2016-02-10 |
| 2016-02-11 |
| 2016-02-12 |
| 2016-02-13 |
| 2016-02-14 |
| 2016-02-16 |
| 2016-02-17 |
| 2016-02-18 |
| 2016-02-19 |
| 2016-02-20 |
| 2016-02-21 |
| 2016-02-22 |
| 2016-02-23 |
| 2016-02-24 |
| 2016-02-25 |
| 2016-02-26 |
| 2016-02-27 |
| 2016-02-28 |
| 2016-02-29 |
| 2016-03-01 |
| 2016-03-02 |
| 2016-03-03 |
| 2016-03-04 |
| 2016-03-05 |
| 2016-03-06 |
| 2016-03-07 |
| 2016-12-20 |
| 2016-12-21 |
| 2016-12-22 |
| 2016-12-23 |
| 2016-12-24 |
| 2016-12-25 |
| 2016-12-26 |
| 2016-12-27 |
| 2016-12-28 |
| 2016-12-29 |
| 2016-12-30 |
| 2016-12-31 |
| 2017-01-01 |
+------------+

Second variant

The first part of the query until CTE_Daily is the same. Then, I'll use a gaps-and-islands approach to find the islands of available dates and calculate their sizes.

WITH
CTE_AllDays
-- list all days and stock IDs between @ParamStartDate and @ParamEndDate
-- for each day and stock indicate whether it is available based on AvailableFromDate
AS
(
    SELECT
        S.StockId
        ,dbo.Calendar.dt
        ,CASE WHEN dbo.Calendar.dt >= S.AvailableFromDate 
            THEN 1 ELSE 0 END AS AvailableStockDay
        -- 1 - available
        -- 0 - not available
    FROM
        @Stocks AS S
        INNER JOIN dbo.Calendar ON
            dbo.Calendar.dt >= @ParamStartDate
            AND dbo.Calendar.dt <= @ParamEndDate
    WHERE
        S.ProductId = @ParamProductID
)
,CTE_BookedDays
-- list all booked (unavailable) days for each stock ID
AS
(
    SELECT
        S.StockId
        ,CA.dt
        ,0 AS AvailableStockDay
        -- 0 - not available
    FROM
        @RentStockOrders AS R
        INNER JOIN @Stocks AS S ON S.StockId = R.StockId
        CROSS APPLY
        (
            SELECT dbo.Calendar.dt
            FROM dbo.Calendar
            WHERE
                dbo.Calendar.dt >= @ParamStartDate
                AND dbo.Calendar.dt <= @ParamEndDate
                AND dbo.Calendar.dt >= R.BeginRentDate
                AND dbo.Calendar.dt <= R.EndRentDate
        ) AS CA
    WHERE
        S.ProductId = @ParamProductID
)
,CTE_Daily
-- combine individual availability flags
-- first: multiply to get the final availability for a stock ID and day
-- second: group further by day and SUM flags
AS
(
    SELECT
        CTE_AllDays.dt
        ,CASE WHEN 
            SUM(
            CTE_AllDays.AvailableStockDay * ISNULL(CTE_BookedDays.AvailableStockDay, 1)
            ) = 0 
        THEN 0 ELSE 1 END AS AvailableDay
        -- day is available, if any stock is available
        -- SUM=0 - not available
        -- SUM>0 - available
    FROM
        CTE_AllDays
        LEFT JOIN CTE_BookedDays ON
            CTE_BookedDays.StockId = CTE_AllDays.StockId AND
            CTE_BookedDays.dt = CTE_AllDays.dt
    GROUP BY
        CTE_AllDays.dt
)
,CTE_RowNumbers
-- calculate two sets of row numbers to isolate consecutive rows with 0s and 1s 
-- (gaps and islands)
AS
(
    SELECT
        dt
        ,AvailableDay
        ,ROW_NUMBER() OVER (ORDER BY dt) AS rn1
        ,ROW_NUMBER() OVER (PARTITION BY AvailableDay ORDER BY dt) AS rn2
    FROM CTE_Daily
)
,CTE_Groups
-- each gaps and island will have the same GroupNumber
-- count the size of the Group
-- number the rows within each Group to find if @ParamDays rows fit into the Group
AS
(
    SELECT
        dt
        ,AvailableDay
        ,GroupNumber
        ,COUNT(*) OVER (PARTITION BY GroupNumber) AS GroupSize
        ,ROW_NUMBER() OVER (PARTITION BY GroupNumber ORDER BY dt) AS GroupRN
    FROM
        CTE_RowNumbers
        CROSS APPLY (SELECT rn1 - rn2 AS GroupNumber) AS CA
)
SELECT
    dt
    --,CASE WHEN AvailableDay = 1 AND GroupSize - GroupRN + 1 >= @ParamDays
    --THEN 1 ELSE 0 END AS AvailableConsecutive
FROM CTE_Groups
WHERE
    CASE WHEN AvailableDay = 1 AND GroupSize - GroupRN + 1 >= @ParamDays
    THEN 1 ELSE 0 END = 0
    -- AvailableConsecutive = 0 to list all unavailable days
ORDER BY dt;

The result is the same as in the first variant, but this variant uses parameter @ParamDays.

To understand how it works, run the query starting with the first CTE, examine the results, then add the next CTE, examine the results and so on.

Best Answer

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