Thanks a lot.. That is what i searched.. In fact your query is very good for little changes, but i will have to use
anothermethod when updating all my rows because the performance is not very good alas.
My data set contains something like 40000 rows to update in 1+ million records and data_raw, data_sys are of type
"real"...The complete update took 40 minutes on a 256Mo, athlon 2400, kernel 2.6 and with no charge during the
executionof the query.
Is this normal ? The number of columns of the table does it matter a lot (the table contains 12 reals and 4 integers)
?
I found that using an intermediate table which stock for every row the value before and the value after helps to gain
speed...But it is not a very nice way i think..
Thanks again :)
Etienne