How to just "link" to some data feed

 Hi,
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 I have some CSV files which I need to link to from within PG
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 From http://darkavngr.blogspot.com/2007/06/importar-datos-externos-nuestra-base-de.html
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 Say, you have the following data feed in /tmp/codigos_postales.csv
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"01000","San Angel","Colonia","Alvaro Obregon","Distrito Federal"
"01010","Los Alpes","Colonia","Alvaro Obregon","Distrito Federal"
"01020","Guadalupe Inn","Colonia","Alvaro Obregon","Distrito Federal"
"01028","Secretaria de Contraloria y Desarrollo Administrativo","Gran
usuario","Alvaro Obregon","Distrito Federal"
"01029","Infonavit","Gran usuario","Alvaro Obregon","Distrito Federal"
"01030","Axotla","Pueblo","Alvaro Obregon","Distrito Federal"
"01030","Florida","Colonia","Alvaro Obregon","Distrito Federal"
"01040","Campestre","Colonia","Alvaro Obregon","Distrito Federal"
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 then you can defined the DB data model as:
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 CREATE TABLE codigos_postales(
  cp char(5),
  asentamiento varchar(120),
  tipo_asentamiento varchar(120),
  municipio varchar(120),
  estado varchar(120)
 );
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 and copy all values into the DB like this:
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 COPY codigos_postales FROM '/tmp/codigos_postales.csv' DELIMITERS ',' CSV;
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 But how do you just link to the data feed effectively keeping it in a
CSV file format not internal to PG?
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 Also I need for all changes to the data to (of course!) be propagated
to the data back end
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 Then you can link to the same data feed from some other engine that
reads in CSV (I think all do or should)
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 How do you link  to a CSV using PG?
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 Thank you
 lbrtchx