In my table I have rows, and each row has some data and its version. 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);
}

I adopted a script from a link below, but it seems to work with known rows. Can it be done for an unknown number of columns (like SELECT * does)? I mean I have multiple tables, and I really don't want to use dynamic SQL or write tens of stored procedures to implement MergeTable1, MergeTable2 and so on.

Current script for a test table:

CREATE TABLE [dbo].[T](
    [id] [int] NOT NULL,
    [A] [int] NULL,
    [B] [int] NULL,
    [C] [int] NULL,
    [Priority] [int] NOT NULL
) ON [PRIMARY]

GO
CREATE UNIQUE CLUSTERED INDEX [ClusteredIndex-20160204-122857] ON [dbo].[T]
(
    [id] ASC,
    [Priority] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
GO
INSERT [dbo].[T] ([id], [A], [B], [C], [Priority]) VALUES (1, NULL, 3, 4, 1)
GO
INSERT [dbo].[T] ([id], [A], [B], [C], [Priority]) VALUES (1, 5, 6, NULL, 2)
GO
INSERT [dbo].[T] ([id], [A], [B], [C], [Priority]) VALUES (1, 8, NULL, NULL, 3)
GO
INSERT [dbo].[T] ([id], [A], [B], [C], [Priority]) VALUES (2, 634, 346, 359, 1)
GO
INSERT [dbo].[T] ([id], [A], [B], [C], [Priority]) VALUES (2, 34, NULL, 734, 2)
GO

input:

id  A       B       C       Priority
1   NULL    3       4       1
1   5       6       NULL    2
1   8       NULL    NULL    3
2   634     346     359     1
2   34      NULL    734     2

desired result:

id  A   B   C   
1   8   6   4   
2   34  346 734