Try this on for size:
WITH LEAVERS AS (

    SELECT    *,
        ROW_NUMBER() OVER(PARTITION BY EmployeeId ORDER BY LeftDate DESC) AS row_num
    FROM dbo.Employee AS E
    WHERE E.Leaver = 1
)

This is a duplicate post.   Please respond only in the original thread, here:

https://www.sqlservercentral.com/Forums/Dialogs/PostDetails.aspx?PostID=1998574

I get the feeling this has to do with running a part of the script separately, which might be getting treated differently than if it were all in the same...

The only question worth asking here at the moment is WHY?   You are already storing dates as integers and depriving yourself of all kinds of cpu time wasted converting back...

The answer here might depend on the nature of your manufacturing process and ordering system.   Some companies go so far as to record multiple SKUs that represent the same item,...

Within SQL Server, you can run a query to check for the existence of a table:
IF OBJECT_ID(N'dbo.SomeTable', N'U')
   BEGIN
    PRINT 'Starting T-SQL actions...'
    --Your T-SQL actions go here
    END;