merging several large CSV's

[McGlinchy, Alistair]

Alex wrote:
> I've been hunting through CPAN for a standard perl module 
> which merges several  large CSVs based on a known key. The 
> nearest I can find is Parse::CSV which lets me stream load 
> single CSVs - but I would then have to implement the merging 
> myself. It seems to me that is a common job.

Maybe your defintion of merge is harder than mine. Modulo the trickiness
of escape conditions for quotes and comma's what's wrong with this?

__CODE__
my $file_one="foo.csv";
my $file_two="bar.csv";
my $key_col_one = 0;  # Column 0 contains the primary key field
my $key_col_two = 2;  # Column 2 contains the foreign key field 

open my $ONE , $file_one or die "Cannot open $file_one : $!"; 
my %store= map { chomp; ( (split/,/)[$key_col_one],  $_ ) } <$ONE>;
close $ONE;

open my $TWO , $file_two or die "Cannot open $file_two : $!"; 
while ( <$TWO> ) {
    chomp;
    my $foreign_key = (split/,/)[$key_col_two];
    print  $store{$foreign_key} , "," , $_, "\n";
}
close $TWO;

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