SELECT (t1.cnt1 + t2.cnt3 - t3.cnt11) FROM table
t1, table t2, table t3 WHERE t1.ColPoint=1 AND
t2.ColPoint=5 AND t3.ColPoint=2 AND t1.id=1 AND
t2.id=t1.id AND t3.id=t1.id
Of course, self joins can be expensive, this grows
in complexity as you need to add/subtract more
counts ,and this is not general.
--Bill
Morten Søndergaard wrote:
> i have a MySQL DB whit this tabel:
>
> Id ColPoint CntDateTime Cnt1 Cnt2
> Cntx..... Cnt32
> 1 1 2001-08-01 00:05:00 12 14
> ....
> 2 1 2001-08-01 00:10:00 11 12
> ....
> 3 1 2001-08-01 00:15:00 10 9
> ....
> 4 1 2001-08-01 00:20:00 0 32
> ....
> 5 1 2001-08-01 00:25:00 6 4
> ....
> 6 1 2001-08-01 00:30:00 14 22
> ....
> 7 1 2001-08-01 00:35:00 11 17
> ....
> .
> .
>
> x1 2 2001-08-01 00:05:00 32 4
> ....
> x2 2 2001-08-01 00:10:00 31 22
> ....
> x3 2 2001-08-01 00:15:00 30 19
> ....
> x4 2 2001-08-01 00:20:00 0 22
> ....
> x5 2 2001-08-01 00:25:00 26 14
> ....
> x6 2 2001-08-01 00:30:00 24 22
> ....
> x7 2 2001-08-01 00:35:00 1 17 ....
>
> .
> .
>
> Ect.
> I am collecting data from 8 collecting points
> whit 32 counters each
>
> I have made a delphi program to show the data in
> bars or curves, but the
> uses shal
> have the opportunite to add and subtrach the
> datas
>
> Exampel for user 1
> ColPoint(Cnt1) +ColPoint5(Cnt3)
> -ColPoint2(Cnt11)
>
> How can i build a sql-string that satisfied this
> need
>
> ----
> ----------------------------------------------------------------
>
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--
Bill Adams
TriQuint Semiconductor
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