existe el comando COPY que permite hacer lo que deseas, busca en la
documentacion vas a encontrar algo como esto
COPY --- copy data between a file and a table
Synopsis
COPY/|tablename|/ [ (/|column|/ [, ...] ) ]
FROM { '/|filename|/' | STDIN }
[ [ WITH ]
[ BINARY ]
[ OIDS ]
[ DELIMITER [ AS ] '/|delimiter|/' ]
[ NULL [ AS ] '/|null string|/' ]
[ CSV [ HEADER ]
[ QUOTE [ AS ] '/|quote|/' ]
[ ESCAPE [ AS ] '/|escape|/' ]
[ FORCE NOT NULL/|column|/ [, ...] ]
COPY {/|tablename|/ [ (/|column|/ [, ...] ) ] | (/|query|/ ) }
TO { '/|filename|/' | STDOUT }
[ [ WITH ]
[ BINARY ]
[ OIDS ]
[ DELIMITER [ AS ] '/|delimiter|/' ]
[ NULL [ AS ] '/|null string|/' ]
[ CSV [ HEADER ]
[ QUOTE [ AS ] '/|quote|/' ]
[ ESCAPE [ AS ] '/|escape|/' ]
[ FORCE QUOTE/|column|/ [, ...] ]