In my table I have rows, and each row has some data and its version. For example

id col1 col2 col3 col4 priority
1  A    NULL B    NULL 1
1  NULL K    NULL NULL 2
1  NULL C    D    NULL 3

the result should be:

id col1 col2 col3 col4
1  A    C    D    NULL 

what logic is used here? It's simple, when column is not-null, it overrides an old value otherwise nothing happens.

Pseudocode (in C#)

var resultTable = new List<Row>();
foreach (var group in table.GroupBy(x => x.ID).Select(g => g.OrderBy(x => x.Priority)))
{
    var row = Row.GetEmpty();
    foreach (var anotherRow in group)
    {
        foreach (var column in group.Columns)
        {
            if (column.GetValue(anotherRow) != null)
                column.SetValue(row, anotherRow);
        }
    }
    resultTable.Add(row);
}

How could it be done with standard SQL features? I saw someone who suggested use SQLCLR, but I want to avoid it if possible.