Unable to merger the value of 1 column that is in multiple tables

Question

I am having trouble updating a column that is found in multiple tables with this script. I would like to use this to prevent duplicate UnitId's throughout the DB. I keep getting this error messages:

The UPDATE statement conflicted with the FOREIGN KEY constraint "Ppt${FA40D62B-B45A-46B2-A5C5-24BA8E5B6318}". The conflict occurred in database "MQS-demo", table "dbo.Unit", column 'UnitID'.

and

The DELETE statement conflicted with the REFERENCE constraint "Ppt${FA40D62B-B45A-46B2-A5C5-24BA8E5B6318}". The conflict occurred in database "MQS-demo", table "dbo.Ppt", column 'UnitID'.

Here is the query

declare @oldUnitID as int=0;
declare @newUnitID as int=0;
declare @temp as TABLE
(
     bincode nvarchar(200),
     cnt     int
)

insert into @temp
select bincode, Count(*)
from   unit
group  by bincode -- HAVING count(*)=2

--select * from @temp

WHILE (SELECT Count(*) from   @temp) > 0 BEGIN

      DECLARE @bincodetodedup as nvarchar(200);

      select top(1) @bincodetodedup = bcode
      from   @temp;

      DECLARE @unitstodedup as TABLE
      (
           unitid int,
           num    int
      )

      insert into @unitstodedup
      select distinct UnitID, ROW_NUMBER() OVER(ORDER BY unitid) as num
      from   unit
      where  bincode = @bincodetodedup
      order  by unitid

      WHILE (SELECT Count(*) from @unitstodedup) > 0 BEGIN
            SELECT TOP(1) @oldUnitID = Unitid
            from   @unitstodedup
            where  num = 1

            SELECT TOP(1) @newUnitID = Unitid
            from   @unitstodedup
            where  num > 1

            update Compatibility
            set    UnitID = @newUnitID
            where  UnitID = @oldUnitID

            update PriceList
            set    UnitID = @newUnitID
            where  UnitID = @oldUnitID

            update Project
            set    UnitID = @newUnitID
            where  UnitID = @oldUnitID

            update ProjectNum
            set    UnitID = @newUnitID
            where  UnitID = @oldUnitID

            update Rate
            set    UnitID = @newUnitID
            where  UnitID = @oldUnitID

            update Resolve
            set    UnitID = @newUnitID
            where  UnitID = @oldUnitID

            update Services
            set    UnitID = @newUnitID
            where  UnitID = @oldUnitID

            update TrainingDate
            set    UnitID = @newUnitID
            where  UnitID = @oldUnitID

            update Form
            set    UnitID = @newUnitID
            where  UnitID = @oldUnitID

            update Ppt
            set    UnitID = @newUnitID
            where  UnitID = @oldUnitID

            --update Unit set UnitID=@newUnitID where UnitID=@oldUnitID
            update Manager
            set    UnitID = @newUnitID
            where  UnitID = @oldUnitID
      END

      DELETE FROM unit
      where  unitid = @oldUnitID

      DELETE TOP(1) from @unitstodedup

      DELETE TOP(1) from @temp
END  

Answer 1

Why do not you do the delete at the end with the variables you are assigning?

    DELETE from @temp where bcode = @bincodetodedup
    DELETE from @unitstodedup where num=1
    DELETE from @unitstodedup where num>1