How to trim first digit off an integer value?
Two options.

First you know what the first column is going to be.  In which case it's a simple

SET Column2 = Column1 - 1000000


or

SET Column2 = Column1 % 1000000


The second has the benefit that the digit could be 1-9 with no problems.

If you have no idea what that first place is going to be and you still only want to get rid of that one value you could do something like this.

declare @test int = 1005
select CAST(SUBSTRING(CAST(@test as varchar(50)),2,999) AS int)


If you have to allow for negative numbers it gets a bit more complicated.

declare @test int = -1005
select CASE WHEN @test &lt; 0 THEN -1 ELSE 1 END *
        CAST(SUBSTRING(CAST(ABS(@test) as varchar(50)),2,999) AS int)


Obviously this could get rather slow for big sets of data.