On May 12, 3:53 pm, "Paul Lautman" <paul.laut...@btinternet.com>
wrote:
> ZeldorBlat wrote:
> > On May 12, 3:44 pm, genzeryk <genze...@gmail.com> wrote:
> >> Hi Folks!
>
> >> I'm a newbie MySQL programmer. While doing my project I have faced
> >> following problem:
>
> >> I have five columns in my table (indexed 'id' and four with numerical
> >> values). I would like to sum the numerical values into a kind of
> >> virtual column and sort the table accordingly to the decreasing
> >> values of the sum (of the virual column).
>
> >> I have searched in numerous tutorials and FAQs but have not found
> >> description of even similar situation.
>
> >> Please help
>
> >> Best regards,
>
> >> Genz
>
> > select id, (a + b + c + d) theSum
> > from someTable
> > order by (a + b + c + d) desc
>
> That seems needlessly wasted on resources, by summing the columns twice.
> Surely either of these 2 would be better:
>
> SELECT
> `id`,
> (`a` + `b` + `c` + `d`) `theSum`
> FROM `someTable`
> ORDER BY `theSum`
>
> or
>
> SELECT
> `id`,
> (`a` + `b` + `c` + `d`) `theSum`
> FROM `someTable`
> ORDER BY 2

Do you know for a fact that MySQL will internally calculate the sums
twice? If the database engine is properly optimized I would guess
that it won't.