Update column with ROW_NUMBER() value

Question

I have a column that I would like to update with a ROW_NUMBER() value partitioned by a specific column.
CREATE TABLE ##tmp (id INT NULL,
value1 VARCHAR(10),
value2 VARCHAR(10))
INSERT INTO ##tmp (value1,
value2)
VALUES ('A', 'asdfasdf'),
('A', 'asdf'),
('A', 'VC'),
('B', 'aasdf'),
('C', 'sdfgs'),
('C', 'xdfbhsdty'),
('C', '23sdgfg'),
('C', '234')
-- update the ID column with the values below
SELECT ROW_NUMBER() OVER (PARTITION BY Value1 ORDER BY Value2),
Value1,
Value2
FROM ##tmp
I have 14 million records.  Can someone explain the best way to do this?  Does the ORDER BY destroy performance for this many records?
Thanks!

Answer 1

CREATE TABLE ##tmp (id INT NULL,
value1 VARCHAR(10),
value2 VARCHAR(10))
INSERT INTO ##tmp (value1,
value2)
VALUES ('A', 'asdfasdf'),
('A', 'asdf'),
('A', 'VC'),
('B', 'aasdf'),
('C', 'sdfgs'),
('C', 'xdfbhsdty'),
('C', '23sdgfg'),
('C', '234')
-- update the ID column with the values below
; with cte as (
SELECT ROW_NUMBER() OVER (PARTITION BY Value1 ORDER BY Value2) as RowNumber,
Value1,
Value2
FROM ##tmp
update cte
set Id = RowNumber;
Russel Loski, MCT, MCSE Data Platform/Business Intelligence. Twitter: @sqlmovers; blog: www.sqlmovers.com