[GRASS5] Re: intersect sites with polygons?
blazek at itc.it
Fri Jul 5 09:18:54 EDT 2002
On Friday 05 July 2002 12:39 pm, Christoph Simon wrote:
> The classic SQL example for an aggregate functin is:
> select max (val) from tab where ...;
> this will return just one row, so it's not going to be typical as an
Select object with category with max value? Not frequent, but say that wee
want see tha last added feature. Should be possible in this way:
where cat = (select max (cat) from tbl);
> OTOH, SQL generally and Postgres in particular allows to
> write SQL and C-language based functions, which can do more or less
> everything: Someone might have a map associated with one or more
> tables and one column for each set of climate data measured. This is
> the point, where she could experiment with different algorithms to
> predict future values, compare it to already known ones and compute an
> index of quality of prediction which would be displayed in the map.
Example of SQL statement for this?
> One thing I use pretty frequently, which is not an aggregate function
> but which also requires access to the first part are more or less
> simple arithmetic operations;
> select inches * 25.4 AS milims from...
Yes, but it does not return list of categories, i guess?
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