On 09/06/09 17:56, A. Marcia BARBOSA wrote:
Hi,
I'm trying to populate a column with 10 raised to the power of the
values in another column:
v.db.update map=ItaReg column=x qcolumn=10^logx
but I get a dbmi protocol error. I've tried using either single or
double quotes with no success. If I use a combination of both, i.e.
"qcolumn= ' 10^logx ' " it doesn't report any error, but doesn't do
the operation either (the column remains unchanged).
It works fine for other operations (e.g. 10*logx), though. Is there
another way in which I should specify the exponentiation?
Which db backend are you using ?
This works for me with a PostgreSQL database:
v.db.addcol ssbel_pg col="test double precision"
v.db.update ssbel_pg col=test value="cat^2" (or qcol="cat^2")
In PostgreSQL there is also power(a,b).
For SQLite the same function is available in the extension-functions.c
available here:
http://sqlite.org/contrib/download/
Moritz
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