DBD::CSV - 如何获取列名？

Question

如何从表中获取列名？我的尝试没有奏效：

#!/usr/bin/env perl
use warnings;
use 5.012;
use DBI;

my $options  = { RaiseError => 1, PrintError => 0, f_ext => ".csv/r" };
my $dbh = DBI->connect( "dbi:CSV:", undef, undef, $options ) or die $DBI::errstr;

my $table = 'test';
$dbh->do( "CREATE TEMP TABLE $table ( id INT, size INT )" );
my $sth = $dbh->prepare( "INSERT INTO $table ( id, size ) VALUES( ?, ? )" );
$sth->execute( 1, 235 );
$sth->execute( 2, 42 );

use Data::Dumper;
say Dumper $dbh->{csv_tables}{$table}{col_names};

$dbh->{csv_tables}{$table} = { skip_first_row => 0 };
$sth = $dbh->prepare( "SELECT * FROM $table" );
$sth->execute;
my @first_row = $sth->fetchrow_array;
say "@first_row\n";

$sth = $dbh->column_info( '', '', $table, '' );
my $ref = $sth->fetchall_arrayref;
say "@$_" for @$ref;


# $VAR1 = undef;
#
# 1 235
#
# Can't call method "fetchall_arrayref" on an undefined value at ./so.pl line 25.

Answer 1

column_info 方法应该由驱动程序实现，如果没有实现，您将得到undef。

我会在您执行第一个查询后查看$sth->{NAME}。

顺便说一句，DBD::CSV 是一个有趣的玩具，但如果您需要一个轻量级的一次性数据库，我强烈建议您改用DBD::SQLite。如果您只需要处理 CSV 数据，那么有几个不错的模块可以为您提供原始访问权限。在这两者之间，很少有 DBD::CSV 有意义的用例。