Tuesday, April 19, 2016

Mutually INCLUSIVE Sets In SQL

SQL is your best friend when you need to find mutually exclusive sets of data – the more conditions you add to your query, the fewer records are returned. But how do you handle mutually INCLUSIVE sets where you want the content of each group to expand as more criteria are met?

 Most people when faced with a request such as that will respond similar to our Mikos (on the left) – with the “You want what? When?” look.

I had the person requesting this code twice demonstrate how he calculated the mutually inclusive set within Excel before taking on the project so I could be certain I understood the logic he was employing to calculate them.

The first demonstration included some “black magic”. During the second demonstration, I asked him to slow down and explain why he was doing what he did.

Terminology

Essentially, they had a many to many relationship between Project Milestones and Contracts for each Project and they needed to be able to accurately report the revenue for these items.
Normally, there’s a one-to-one or one-to-many relationship between Milestones and Contracts for Projects (at least in the software that I have worked with), so this was to handle the exceptional relationship so they could calculate Project costs and revenue appropriately.
Project – A project – like “build a house”
Project Milestone – Completion of certain tasks for a project – like Painting or Install Carpeting
Contract – the agreement between Customer & the subcontractor doing the work – the painter who also installs carpeting
Reporting Groups – Mutually inclusive sets related to the Milestone & Contract combinations – one reporting group contains all milestones for each Contract as well as all Contracts for each milestone

Algorithm

Determining the correct Reporting Group value is a multi-step process calculated over all Contracts and Milestones associated to the Project.
  1. Sort by Milestone
  2. Assign First-pass group value using DENSE_RANK() OVER (ORDER BY Milestone)
  3. Sort By Contract
  4. For each Contract with multiple Milestones, if the grouping values differ, assign all instances of the grouping value to the lowest value (Example: In Item 16, there are two Milestones. One has Grouping Value 4 & other has Grouping Value 6. Set all Grouping Value 6 instances = 4. Repeat for each Contract where a similar situation exists)
  5. Sort by Grouping Value
  6. Update Grouping Values so that any gaps in the sequence are closed (Example: Grouping Value 6 was removed in an earlier step, so all items with Grouping Value 7 become 6, then all the 8s become 7, etc. so that the Grouping Values are consecutive.)

Code

I found that the only way to reproduce the results was to loop through the data sets similar to the demonstrated method which includes suspiciously redundant code required to produce the “correct-according-to-the-customer” results.
The following may not be ideal SQL, but I found that it returned results exactly matching several examples provided by the Customer. Yes, the seemingly redundant updates are necessary because without them the final output does not match his final results. I have not found any alternative method to replicate the same results more efficiently.
Please note that I’ve simplified the content:
  • Only include what was directly relevant to the calculation of the mutually inclusive data sets
  • The sample dataset that is entered into the @ContractMilestones table is not nearly close to the 100+ line examples given to me
  • I have excluded any direct references to proprietary tables
Please note that the final insert has been commented out since the “FinalReportingGroups” table was not defined in the code, but it exists within the Customer’s database to store the Reporting Groups thus calculated. I’m sure that Readers of this post understand that they only need to view the final results of the calculations since updating the final table would depend upon their own personal database schema.)

    DECLARE @ContractMilestones TABLE (
        Co TINYINT
        ,Project VARCHAR(10)
        ,[Contract] VARCHAR(16)
        ,Milestone VARCHAR(20)
        )
       
INSERT @ContractMilestones (Co, Project, [Contract], Milestone)
VALUES
     ( 102,'Test', '5','493')
    ,( 102,'Test', '1.01','111')
    ,( 102,'Test', '1.01', '211')
    ,( 102,'Test', '1.01', '311')
    ,( 102,'Test', '2.02', '111')
    ,( 102,'Test', '3.01', '211')

    DECLARE @ReportingGroups TABLE (
        Co TINYINT
        ,Project VARCHAR(10)
        ,Milestone VARCHAR(20)
        ,[Contract] VARCHAR(16)
        ,MilestoneRptGroup INT
        ,ContractGrouping INT
        ,FinalGroup INT
        );

    WITH preranked (
        Co
        ,Project
        ,Milestone
        ,[Contract]
        ,MilestoneRptGroup
        )
    AS (
        SELECT Co
            ,Project
            ,Milestone
            ,[Contract]
            ,DENSE_RANK() OVER (
                PARTITION BY Co
                ,Project ORDER BY Co
                    ,Project
                    ,Milestone
                ) AS MilestoneRptGroup
        FROM @ContractMilestones
        )
        ,contractgroupd (
        Co
        ,Project
        ,Milestone
        ,[Contract]
        ,MilestoneRptGroup
        ,ContractGrouping
        )
    AS (
        SELECT Co
            ,Project
            ,Milestone
            ,[Contract]
            ,MilestoneRptGroup
            ,min(MilestoneRptGroup) OVER (
                PARTITION BY [Contract] ORDER BY [Contract] DESC
                ) AS ContractGrouping
        FROM preranked
        )
    INSERT @ReportingGroups (
        Co
        ,Project
        ,Milestone
        ,[Contract]
        ,MilestoneRptGroup
        ,ContractGrouping
        ,FinalGroup
        )
    SELECT Co
        ,Project
        ,Milestone
        ,[Contract]
        ,MilestoneRptGroup
        ,ContractGrouping
        ,DENSE_RANK() OVER (
            ORDER BY Co
                ,Project
                ,ContractGrouping
            ) AS FinalGroup
    FROM contractgroupd
    ORDER BY FinalGroup

    DECLARE @ItemGrouping INT
    DECLARE @MilestoneGroup TABLE (MilestoneRptGroup INT)
    DECLARE @ContractGroup TABLE (ContractRptGroup INT)

    SELECT @ItemGrouping = min(FinalGroup)
    FROM @ReportingGroups

    WHILE @ItemGrouping IS NOT NULL
    BEGIN
        INSERT @MilestoneGroup (MilestoneRptGroup)
        SELECT DISTINCT MilestoneRptGroup
        FROM @ReportingGroups
        WHERE FinalGroup = @ItemGrouping

        UPDATE @ReportingGroups
        SET FinalGroup = @ItemGrouping
            ,MilestoneRptGroup = @ItemGrouping
        WHERE MilestoneRptGroup IN (
                SELECT MilestoneRptGroup
                FROM @MilestoneGroup
                )

        DELETE
        FROM @MilestoneGroup

        INSERT @ContractGroup (ContractRptGroup)
        SELECT DISTINCT ContractGrouping
        FROM @ReportingGroups
        WHERE FinalGroup = @ItemGrouping

        UPDATE @ReportingGroups
        SET FinalGroup = @ItemGrouping
            ,ContractGrouping = @ItemGrouping
        WHERE ContractGrouping IN (
                SELECT ContractRptGroup
                FROM @ContractGroup
                )

        DELETE
        FROM @ContractGroup

        INSERT @MilestoneGroup (MilestoneRptGroup)
        SELECT DISTINCT MilestoneRptGroup
        FROM @ReportingGroups
        WHERE FinalGroup = @ItemGrouping

        UPDATE @ReportingGroups
        SET FinalGroup = @ItemGrouping
            ,MilestoneRptGroup = @ItemGrouping
        WHERE MilestoneRptGroup IN (
                SELECT MilestoneRptGroup
                FROM @MilestoneGroup
                )

        DELETE
        FROM @MilestoneGroup

        INSERT @ContractGroup (ContractRptGroup)
        SELECT DISTINCT ContractGrouping
        FROM @ReportingGroups
        WHERE FinalGroup = @ItemGrouping

        UPDATE @ReportingGroups
        SET FinalGroup = @ItemGrouping
            ,ContractGrouping = @ItemGrouping
        WHERE ContractGrouping IN (
                SELECT ContractRptGroup
                FROM @ContractGroup
                )

        DELETE
        FROM @ContractGroup

        SELECT @ItemGrouping = min(FinalGroup)
        FROM @ReportingGroups
        WHERE FinalGroup > @ItemGrouping
    END;

-- This is the final table that holds the data we've retrieved
-- insert commented out so we can do a simple select.   
  --  INSERT FinalReportingGroups (
  --      Co
  --     ,Project
  --     ,[Contract]
  --     ,ReportingGroup
  --     ,Milestone
  --     )
    SELECT Co
        ,Project
        ,[Contract]
        ,DENSE_RANK() OVER (
            ORDER BY Co
                ,Project
                ,ContractGrouping
            ) AS ReportingGroup
        ,Milestone
    FROM @ReportingGroups
    ORDER BY Co
        ,Project
        ,[Contract]
        ,Milestone



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