On Wed, Dec 02, 2020 at 11:02:07PM +0100, Thomas Kellerer <shammat@xxxxxxx> wrote: > guyren@xxxxxxxxxx schrieb am 02.12.2020 um 21:27: > > The Halloween problem is that it is a challenge for the database if > > you’re updating a field that is also in the WHERE clause of the same > > query. > > > > I just saw a presentation from someone about how in SQL Server he > > recommended writing changes to a temp table and then writing them to > > the table as being much more efficient. > > It sounds strange to me, that this _is_ actually a problem. > > Why exactly is that a problem in SQL Server? > And what are the consequences if you do it nevertheless. According to wikipedia, this problem was discovered on Halloween day, 1976. I find it hard to believe that any database would still exhibit that behaviour 44 years later. cheers, raf
