Hurtigere måde at opdatere et felt

Opdateringen sker vha. et script i SQL Server Analyzer og tager ca. 2½ time at gennemløbe ca. 430.000 poster fordelt i 6 tabeller.
(ER det nødvendigt at bruge cursors?)

Script:

USE myDatabase

SET DATEFIRST 1 

DECLARE
  @Tabel_var as varchar(255),
  @Dato_var as varchar(255)

DECLARE myDatabase_cursor CURSOR FOR
SELECT Dato
FROM [myTAble]

OPEN myTable_cursor

FETCH NEXT FROM myDatabase_cursor
INTO @Dato_var

WHILE @@FETCH_STATUS = 0
  BEGIN
    UPDATE [myTable] SET UGE = DATEPART(week, @Dato_var) WHERE Dato = @Dato_var
  FETCH NEXT FROM myDatabase_cursor
  INTO @Dato_var
END

CLOSE myDatabase_cursor
DEALLOCATE myDatabase_cursor