Want to combine two rows into one row
The simplest way to merge rows is with an aggregate function such as MIN/MAX. These functions will ignore nulls (see MSDN) and can operate similarly to ISNULL/COALESCE with aggregation. For example:

SELECT
  EmployeeNo,
  MAX(Column1) AS Column1,
  MAX(Column2) AS Column2
FROM MyTable
GROUP BY EmployeeNo


This will return the sample desired results. If your only goal is to merge columns with null values into rows with data in those columns, it doesn't matter whether you use MIN or MAX - the result set will be the same.