[postgis-users] UPDATE table to a joined query...

[Mike Leahy]

Sorry - this was meant for the PGSQL users list...

Quoting Mike Leahy <mgleahy at fes.uwaterloo.ca>:

> Hello all,
> 
> This question is related to updating tables - is there any way to calculate
> or 
> update the values in a column in a table to the values in a field produced by
> 
> a query result?  An example of what I'm trying to do is below:
> 
> update (tbl_ind_mananas LEFT JOIN (select count(*) as count, (dubicacion || 
> zona || manzana) as cod_manzana from tbl_censo_poblacion_1993 group by 
> dubicacion, zona, manzana) tbl1 on relacion = cod_manzana) as tbl2 set 
> poblacion = count;
> 
> Basically I have a table (tbl_ind_manzanas) with a unique code (relacion)
> that 
> can be linked to a field in the query result (cod_manzana).  I want to update
> 
> a field in the table with the count(*) result in the query.  The update 
> statement (as I have attempted it above) doesn't work...it seems that I can
> do 
> nothing but directly update the values in a table.  As soon as I try to
> supply 
> anything other than just a table to the update statement, it doesn't like
> it.
> 
> I'm sure others have experience with this issue...it seems to me that there 
> would be many cases where such an approach would be useful.  I'm hoping 
> there's another method that I might be able to use that could accomplish 
> essentially the same result.  Any suggestions are greatly appreciated.
> 
> Kind regards,
> Mike
> 
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