In Power Query, how do you combine Columns 1 and 2 to produce Column 3 as in the example below. The value 999999999 is stored as text.
[TABLE="width: 293"]
<colgroup><col><col><col></colgroup><tbody>[TR]
[TD]Col1[/TD]
[TD]Col2[/TD]
[TD]Col3[/TD]
[/TR]
[TR]
[TD]999999999[/TD]
[TD]999999999[/TD]
[TD]999999999[/TD]
[/TR]
[TR]
[TD]null[/TD]
[TD]#N/A[/TD]
[TD]null[/TD]
[/TR]
[TR]
[TD]999999999[/TD]
[TD]#N/A[/TD]
[TD]999999999[/TD]
[/TR]
[TR]
[TD]null[/TD]
[TD]999999999[/TD]
[TD]999999999[/TD]
[/TR]
</tbody>[/TABLE]
[TABLE="width: 293"]
<colgroup><col><col><col></colgroup><tbody>[TR]
[TD]Col1[/TD]
[TD]Col2[/TD]
[TD]Col3[/TD]
[/TR]
[TR]
[TD]999999999[/TD]
[TD]999999999[/TD]
[TD]999999999[/TD]
[/TR]
[TR]
[TD]null[/TD]
[TD]#N/A[/TD]
[TD]null[/TD]
[/TR]
[TR]
[TD]999999999[/TD]
[TD]#N/A[/TD]
[TD]999999999[/TD]
[/TR]
[TR]
[TD]null[/TD]
[TD]999999999[/TD]
[TD]999999999[/TD]
[/TR]
</tbody>[/TABLE]