“无法在DBD :: CSV中找到FROM子句中的表名”错误

Question

I'm trying to use a UNION statement in DBI to combine two CSV files:

#!/usr/bin/perl -w

use strict;
use DBI;

my $dbh = DBI->connect ("dbi:CSV:") 
    or die "Cannot connect to the CSV file: $DBI::errstr()";
$dbh->{RaiseError} = 1;
$dbh->{TraceLevel} = 0;

my $query = "select * from file.csv UNION select * from output.csv";
my $sth = $dbh->prepare ($query);
$sth->execute ();
$sth->dump_results();
$sth->finish();
$dbh->disconnect();

However, I get the following errors:

Can't find table names in FROM clause! at C:/Perl64/site/lib/SQL/Statement.pm line 88.
DBD::CSV::db prepare failed: Can't find table names in FROM clause! at C:/Perl64 /site/lib/SQL/Statement.pm line 88.
[for Statement "select * from file.csv UNION select * from output.csv"] at CSV. pl line 15.
DBD::CSV::db prepare failed: Can't find table names in FROM clause! at C:/Perl64 /site/lib/SQL/Statement.pm line 88.
[for Statement "select * from file.csv UNION select * from output.csv"] at CSV. pl line 15.

I updated SQL::Statement and SQL::Parse as suggested elsewhere but that didn't fix the issue. I'm running on Windows 8.1. What is causing the errors?

Answer 1

Drop .csv extensions from query and make sure your files are in current dir:

my $query = "select * from file UNION select * from output";

You can also explicitly set folder with csv files,

my $dbh = DBI->connect ("dbi:CSV:", "", "", {
    f_dir => 'C:\path_to_csv',
});

Answer 2

DBD::CSV uses SQL::Statement as its SQL engine. SQL::Statement only supports a subset of SQL commands , which does not include UNION .

As an alternative, why not simply concatenate the two files?