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DBD::CSV(3)	      User Contributed Perl Documentation	   DBD::CSV(3)

NAME
       DBD::CSV - DBI driver for CSV files

SYNOPSIS
	   use DBI;
	   # See "Creating database handle" below
	   $dbh = DBI->connect ("dbi:CSV:") or
	       die "Cannot connect: $DBI::errstr";

	   # Simple statements
	   $dbh->do ("CREATE TABLE a (id INTEGER, name CHAR (10))") or
	       die "Cannot prepare: " . $dbh->errstr ();

	   # Selecting
	   $dbh->{RaiseError} = 1;
	   my $sth = $dbh->prepare ("select * from foo");
	   $sth->execute;
	   while (my @row = $sth->fetchrow_array) {
	       print "id: $row[0], name: $row[1]\n";
	       }

	   # Updates
	   my $sth = $dbh->prepare ("UPDATE a SET name = ? WHERE id = ?");
	   $sth->execute ("DBI rocks!", 1);
	   $sth->finish;

	   $dbh->disconnect;

DESCRIPTION
       The DBD::CSV module is yet another driver for the DBI (Database
       independent interface for Perl). This one is based on the SQL "engine"
       SQL::Statement and the abstract DBI driver DBD::File and implements
       access to so-called CSV files (Comma Separated Values). Such files are
       often used for exporting MS Access and MS Excel data.

       See DBI for details on DBI, SQL::Statement for details on
       SQL::Statement and DBD::File for details on the base class DBD::File.

   Prerequisites
       The only system dependent feature that DBD::File uses, is the "flock
       ()" function. Thus the module should run (in theory) on any system with
       a working "flock ()", in particular on all Unix machines and on Windows
       NT. Under Windows 95 and MacOS the use of "flock ()" is disabled, thus
       the module should still be usable.

       Unlike other DBI drivers, you don't need an external SQL engine or a
       running server. All you need are the following Perl modules, available
       from any CPAN mirror, for example

	 http://search.cpan.org/

       DBI The DBI (Database independent interface for Perl), version 1.00 or
	   a later release

       DBD::File
	   This is the base class for DBD::CSV, and it is part of the DBI
	   distribution. As DBD::CSV requires version 0.38 or newer for
	   DBD::File it effectively requires DBI version 1.611 or newer.

       SQL::Statement
	   A simple SQL engine. This module defines all of the SQL syntax for
	   DBD::CSV, new SQL support is added with each release so you should
	   look for updates to SQL::Statement regularly.

	   It is possible to run "DBD::CSV" without this module if you define
	   the environment variable $DBI_SQL_NANO to 1. This will reduce the
	   SQL support a lot though. See DBI::SQL::Nano for more details. Note
	   that the test suite does not test in this mode!

       Text::CSV_XS
	   This module is used for writing rows to or reading rows from CSV
	   files.

   Installation
       Installing this module (and the prerequisites from above) is quite
       simple.	The simplest way is to install the bundle:

	   $ cpan Bundle::CSV

       Alternatively, you can name them all

	   $ cpan Text::CSV_XS DBI DBD::CSV

       or even trust "cpan" to resolve all dependencies for you:

	   $ cpan DBD::CSV

       If you cannot, for whatever reason, use cpan, fetch all modules from
       CPAN, and build with a sequence like:

	   gzip -d < DBD-CSV-0.28.tgz | tar xf -

       (this is for Unix users, Windows users would prefer WinZip or something
       similar) and then enter the following:

	   cd DBD-CSV-0.28
	   perl Makefile.PL
	   make test

       If any tests fail, let us know. Otherwise go on with

	   make install UNINST=1

       Note that you almost definitely need root or administrator permissions.
       If you don't have them, read the ExtUtils::MakeMaker man page for
       details on installing in your own directories. ExtUtils::MakeMaker.

   Supported SQL Syntax
       All SQL processing for DBD::CSV is done by the SQL::Statement module.
       Features include joins, aliases, built-in and user-defined functions,
       and more.  See SQL::Statement::Syntax for a description of the SQL
       syntax supported in DBD::CSV.

       Table names are case insensitive unless quoted.

Using DBD::CSV with DBI
       For most things, DBD-CSV operates the same as any DBI driver.  See DBI
       for detailed usage.

   Creating a database handle (connect)
       Creating a database handle usually implies connecting to a database
       server.	Thus this command reads

	   use DBI;
	   my $dbh = DBI->connect ("dbi:CSV:", "", "", {
	       f_dir => "/home/user/folder",
	       });

       The directory tells the driver where it should create or open tables
       (a.k.a.	files). It defaults to the current directory, so the following
       are equivalent:

	   $dbh = DBI->connect ("dbi:CSV:");
	   $dbh = DBI->connect ("dbi:CSV:", undef, undef, { f_dir => "." });
	   $dbh = DBI->connect ("dbi:CSV:f_dir=.");

       We were told, that VMS might - for whatever reason - require:

	   $dbh = DBI->connect ("dbi:CSV:f_dir=");

       The preferred way of passing the arguments is by driver attributes:

	   # specify most possible flags via driver flags
	   $dbh = DBI->connect ("dbi:CSV:", undef, undef, {
	       f_schema		=> undef,
	       f_dir		=> "data",
	       f_ext		=> ".csv/r",
	       f_lock		=> 2,
	       f_encoding	=> "utf8",

	       csv_eol		=> "\r\n",
	       csv_sep_char	=> ",",
	       csv_quote_char	=> '"',
	       csv_escape_char	=> '"',
	       csv_class	=> "Text::CSV_XS",
	       csv_null		=> 1,
	       csv_tables	=> {
		   info => { file => "info.csv" }
		   },

	       RaiseError	=> 1,
	       PrintError	=> 1,
	       FetchHashKeyName => "NAME_lc",
	       }) or die $DBI::errstr;

       but you may set these attributes in the DSN as well, separated by
       semicolons.  Pay attention to the semi-colon for "csv_sep_char" (as
       seen in many CSV exports from MS Excel) is being escaped in below
       example, as is would otherwise be seen as attribute separator:

	   $dbh = DBI->connect (
	       "dbi:CSV:f_dir=$ENV{HOME}/csvdb;f_ext=.csv;f_lock=2;" .
	       "f_encoding=utf8;csv_eol=\n;csv_sep_char=\\;;" .
	       "csv_quote_char=\";csv_escape_char=\\;csv_class=Text::CSV_XS;" .
	       "csv_null=1") or die $DBI::errstr;

       Using attributes in the DSN is easier to use when the DSN is derived
       from an outside source (environment variable, database entry, or
       configure file), whereas using all entries in the attribute hash is
       easier to read and to maintain.

   Creating and dropping tables
       You can create and drop tables with commands like the following:

	   $dbh->do ("CREATE TABLE $table (id INTEGER, name CHAR (64))");
	   $dbh->do ("DROP TABLE $table");

       Note that currently only the column names will be stored and no other
       data.  Thus all other information including column type (INTEGER or
       CHAR (x), for example), column attributes (NOT NULL, PRIMARY KEY, ...)
       will silently be discarded. This may change in a later release.

       A drop just removes the file without any warning.

       See DBI for more details.

       Table names cannot be arbitrary, due to restrictions of the SQL syntax.
       I recommend that table names are valid SQL identifiers: The first
       character is alphabetic, followed by an arbitrary number of
       alphanumeric characters. If you want to use other files, the file names
       must start with "/", "./" or "../" and they must not contain white
       space.

   Inserting, fetching and modifying data
       The following examples insert some data in a table and fetch it back:
       First all data in the string:

	   $dbh->do ("INSERT INTO $table VALUES (1, ".
		      $dbh->quote ("foobar") . ")");

       Note the use of the quote method for escaping the word "foobar". Any
       string must be escaped, even if it does not contain binary data.

       Next an example using parameters:

	   $dbh->do ("INSERT INTO $table VALUES (?, ?)", undef, 2,
		     "It's a string!");

       Note that you don't need to use the quote method here, this is done
       automatically for you. This version is particularly well designed for
       loops. Whenever performance is an issue, I recommend using this method.

       You might wonder about the "undef". Don't wonder, just take it as it
       is. :-) It's an attribute argument that I have never ever used and will
       be parsed to the prepare method as a second argument.

       To retrieve data, you can use the following:

	   my $query = "SELECT * FROM $table WHERE id > 1 ORDER BY id";
	   my $sth   = $dbh->prepare ($query);
	   $sth->execute ();
	   while (my $row = $sth->fetchrow_hashref) {
	       print "Found result row: id = ", $row->{id},
		     ", name = ", $row->{name};
	       }
	   $sth->finish ();

       Again, column binding works: The same example again.

	   my $sth = $dbh->prepare (qq;
	       SELECT * FROM $table WHERE id > 1 ORDER BY id;
	       ;);
	   $sth->execute;
	   my ($id, $name);
	   $sth->bind_columns (undef, \$id, \$name);
	   while ($sth->fetch) {
	       print "Found result row: id = $id, name = $name\n";
	       }
	   $sth->finish;

       Of course you can even use input parameters. Here's the same example
       for the third time:

	   my $sth = $dbh->prepare ("SELECT * FROM $table WHERE id = ?");
	   $sth->bind_columns (undef, \$id, \$name);
	   for (my $i = 1; $i <= 2; $i++) {
	       $sth->execute ($id);
	       if ($sth->fetch) {
		   print "Found result row: id = $id, name = $name\n";
		   }
	       $sth->finish;
	       }

       See DBI for details on these methods. See SQL::Statement for details on
       the WHERE clause.

       Data rows are modified with the UPDATE statement:

	   $dbh->do ("UPDATE $table SET id = 3 WHERE id = 1");

       Likewise you use the DELETE statement for removing rows:

	   $dbh->do ("DELETE FROM $table WHERE id > 1");

   Error handling
       In the above examples we have never cared about return codes. Of
       course, this cannot be recommended. Instead we should have written (for
       example):

	   my $sth = $dbh->prepare ("SELECT * FROM $table WHERE id = ?") or
	       die "prepare: " . $dbh->errstr ();
	   $sth->bind_columns (undef, \$id, \$name) or
	       die "bind_columns: " . $dbh->errstr ();
	   for (my $i = 1; $i <= 2; $i++) {
	       $sth->execute ($id) or
		   die "execute: " . $dbh->errstr ();
	       $sth->fetch and
		   print "Found result row: id = $id, name = $name\n";
	       }
	   $sth->finish ($id) or die "finish: " . $dbh->errstr ();

       Obviously this is tedious. Fortunately we have DBI's RaiseError
       attribute:

	   $dbh->{RaiseError} = 1;
	   $@ = "";
	   eval {
	       my $sth = $dbh->prepare ("SELECT * FROM $table WHERE id = ?");
	       $sth->bind_columns (undef, \$id, \$name);
	       for (my $i = 1; $i <= 2; $i++) {
		   $sth->execute ($id);
		   $sth->fetch and
		       print "Found result row: id = $id, name = $name\n";
		   }
	       $sth->finish ($id);
	       };
	   $@ and die "SQL database error: $@";

       This is not only shorter, it even works when using DBI methods within
       subroutines.

DBI database handle attributes
   Metadata
       The following attributes are handled by DBI itself and not by
       DBD::File, thus they all work as expected:

	   Active
	   ActiveKids
	   CachedKids
	   CompatMode		  (Not used)
	   InactiveDestroy
	   Kids
	   PrintError
	   RaiseError
	   Warn			  (Not used)

       The following DBI attributes are handled by DBD::File:

       AutoCommit
	   Always on

       ChopBlanks
	   Works

       NUM_OF_FIELDS
	   Valid after "$sth->execute"

       NUM_OF_PARAMS
	   Valid after "$sth->prepare"

       NAME
       NAME_lc
       NAME_uc
	   Valid after "$sth->execute"; undef for Non-Select statements.

       NULLABLE
	   Not really working. Always returns an array ref of one's, as
	   DBD::CSV does not verify input data. Valid after "$sth->execute";
	   undef for non-Select statements.

       These attributes and methods are not supported:

	   bind_param_inout
	   CursorName
	   LongReadLen
	   LongTruncOk

DBD-CSV specific database handle attributes
       In addition to the DBI attributes, you can use the following dbh
       attributes:

       f_dir
	   This attribute is used for setting the directory where CSV files
	   are opened. Usually you set it in the dbh, it defaults to the
	   current directory ("."). However, it is overwritable in the
	   statement handles.

       f_ext
	   This attribute is used for setting the file extension.

       f_schema
	   This attribute allows you to set the database schema name. The
	   default is to use the owner of "f_dir". "undef" is allowed, but not
	   in the DSN part.

	       my $dbh = DBI->connect ("dbi:CSV:", "", "", {
		   f_schema => undef,
		   f_dir    => "data",
		   f_ext    => ".csv/r",
		   }) or die $DBI::errstr;

       f_encoding
	   This attribute allows you to set the encoding of the data. With
	   CSV, it is not possible to set (and remember) the encoding on a
	   per-field basis, but DBD::File now allows to set the encoding of
	   the underlying file. If this attribute is not set, or undef is
	   passed, the file will be seen as binary.

       f_lock
	   With this attribute, you can force locking mode (if locking is
	   supported at all) for opening tables. By default, tables are opened
	   with a shared lock for reading, and with an exclusive lock for
	   writing. The supported modes are:

	   0 Force no locking at all.

	   1 Only shared locks will be used.

	   2 Only exclusive locks will be used.

	   But see "KNOWN BUGS" in DBD::File.

       csv_eol
       csv_sep_char
       csv_quote_char
       csv_escape_char
       csv_class
       csv_csv
	   The attributes csv_eol, csv_sep_char, csv_quote_char and
	   csv_escape_char are corresponding to the respective attributes of
	   the Text::CSV_XS object. You want to set these attributes if you
	   have unusual CSV files like /etc/passwd or MS Excel generated CSV
	   files with a semicolon as separator. Defaults are "\015\012", ';',
	   '"' and '"', respectively.

	   The csv_eol attribute defines the end-of-line pattern, which is
	   better known as a record separator pattern since it separates
	   records.  The default is windows-style end-of-lines "\015\012" for
	   output (writing) and unset for input (reading), so if on unix you
	   may want to set this to newline ("\n") like this:

	     $dbh->{csv_eol} = "\n";

	   It is also possible to use multi-character patterns as record
	   separators.	For example this file uses newlines as field
	   separators (sep_char) and the pattern "\n__ENDREC__\n" as the
	   record separators (eol):

	     name
	     city
	     __ENDREC__
	     joe
	     seattle
	     __ENDREC__
	     sue
	     portland
	     __ENDREC__

	   To handle this file, you'd do this:

	     $dbh->{eol}      = "\n__ENDREC__\n" ,
	     $dbh->{sep_char} = "\n"

	   The attributes are used to create an instance of the class
	   csv_class, by default Text::CSV_XS. Alternatively you may pass an
	   instance as csv_csv, the latter takes precedence. Note that the
	   binary attribute must be set to a true value in that case.

	   Additionally you may overwrite these attributes on a per-table base
	   in the csv_tables attribute.

       csv_null
	   With this option set, all new statement handles will set
	   "always_quote" and "blank_is_undef" in the CSV parser and writer,
	   so it knows how to distinguish between the empty string and "undef"
	   or "NULL". You cannot reset it with a false value. You can pass it
	   to connect, or set it later:

	     $dbh = DBI->connect ("dbi:CSV:", "", "", { csv_null => 1 });

	     $dbh->{csv_null} = 1;

       csv_tables
	   This hash ref is used for storing table dependent metadata. For any
	   table it contains an element with the table name as key and another
	   hash ref with the following attributes:

       csv_*
	   All other attributes that start with "csv_" and are not described
	   above will be passed to "Text::CSV_XS" (without the "csv_" prefix).
	   these extra options are most likely to be only useful for reading
	   (select) handles. Examples:

	     $dbh->{csv_allow_whitespace}    = 1;
	     $dbh->{csv_allow_loose_quotes}  = 1;
	     $dbh->{csv_allow_loose_escapes} = 1;

	   See the "Text::CSV_XS" documentation for the full list and the
	   documentation.

	   file
	       The tables file name; defaults to

		   "$dbh->{f_dir}/$table"

	   eol
	   sep_char
	   quote_char
	   escape_char
	   class
	   csv These correspond to the attributes csv_eol, csv_sep_char,
	       csv_quote_char, csv_escape_char, csv_class and csv_csv.	The
	       difference is that they work on a per-table base.

	   col_names
	   skip_first_row
	       By default DBD::CSV assumes that column names are stored in the
	       first row of the CSV file and sanitizes them (see "raw_header"
	       below). If this is not the case, you can supply an array ref of
	       table names with the col_names attribute. In that case the
	       attribute skip_first_row will be set to FALSE.

	       If you supply an empty array ref, the driver will read the
	       first row for you, count the number of columns and create
	       column names like "col0", "col1", ...

	   raw_header
	       Due to the SQL standard, field names cannot contain special
	       characters like a dot ("."). Following the approach of
	       mdb_tools, all these tokens are translated to an underscore
	       ("_") when reading the first line of the CSV file, so all field
	       names are `sanitized'. If you do not want this to happen, set
	       "raw_header" to a true value. DBD::CSV cannot guarantee that
	       any part in the toolchain will work if field names have those
	       characters, and the chances are high that the SQL statements
	       will fail.

       It's strongly recommended to check the attributes supported by
       "Metadata" in DBD::File.

       Example: Suggest you want to use /etc/passwd as a CSV file. :-) There
       simplest way is:

	   use DBI;
	   my $dbh = DBI->connect ("dbi:CSV:", undef, undef, {
	       f_dir	       => "/etc",
	       csv_sep_char    => ":",
	       csv_quote_char  => undef,
	       csv_escape_char => undef,
	       });
	   $dbh->{csv_tables}{passwd} = {
	       col_names => [qw( login password uid gid realname
				 directory shell )];
	       };
	   $sth = $dbh->prepare ("SELECT * FROM passwd");

       Another possibility where you leave all the defaults as they are and
       overwrite them on a per table base:

	   require DBI;
	   my $dbh = DBI->connect ("dbi:CSV:");
	   $dbh->{csv_tables}{passwd} = {
	       eol	   => "\n",
	       sep_char	   => ":",
	       quote_char  => undef,
	       escape_char => undef,
	       file	   => "/etc/passwd",
	       col_names   => [qw( login password uid gid
				   realname directory shell )],
	       };
	   $sth = $dbh->prepare ("SELECT * FROM passwd");

   Driver private methods
       These methods are inherited from DBD::File:

       data_sources
	   The "data_sources" method returns a list of sub-directories of the
	   current directory in the form "dbi:CSV:directory=$dirname".

	   If you want to read the sub-directories of another directory, use

	       my $drh	= DBI->install_driver ("CSV");
	       my @list = $drh->data_sources (f_dir => "/usr/local/csv_data");

       list_tables
	   This method returns a list of file names inside $dbh->{directory}.
	   Example:

	       my $dbh	= DBI->connect ("dbi:CSV:directory=/usr/local/csv_data");
	       my @list = $dbh->func ("list_tables");

	   Note that the list includes all files contained in the directory,
	   even those that have non-valid table names, from the view of SQL.
	   See "Creating and dropping tables" above.

KNOWN ISSUES
       ยท   The module is using flock () internally. However, this function is
	   not available on platforms. Using flock () is disabled on MacOS and
	   Windows 95: There's no locking at all (perhaps not so important on
	   these operating systems, as they are for single users anyways).

TODO
       Tests
	   Aim for a full 100% code coverage

	    - eol      Make tests for different record separators.
	    - csv_xs   Test with a variety of combinations for
		       sep_char, quote_char, and escape_char testing
	    - quoting  $dbh->do ("drop table $_") for DBI-tables ();
	    - errors   Make sure that all documented exceptions are tested.
		       . write to write-protected file
		       . read from badly formatted csv
		       . pass bad arguments to csv parser while fetching

	   Add tests that specifically test DBD::File functionality where that
	   is useful.

       RT  Attack all open DBD::CSV bugs in RT

       CPAN::Forum
	   Attack all items in http://www.cpanforum.com/dist/DBD-CSV

       Documentation
	   Expand on error-handling, and document all possible errors.	Use
	   Text::CSV_XS::error_diag () wherever possible.

       Debugging
	   Implement and document dbd_verbose.

       Data dictionary
	   Investigate the possibility to store the data dictionary in a file
	   like .sys$columns that can store the field attributes (type, key,
	   nullable).

       Examples
	   Make more real-life examples from the docs in examples/

SEE ALSO
       DBI, Text::CSV_XS, SQL::Statement, DBI::SQL::Nano

       For help on the use of DBD::CSV, see the DBI users mailing list:

	 http://lists.cpan.org/showlist.cgi?name=dbi-users

       For general information on DBI see

	 http://dbi.perl.org/ and http://faq.dbi-support.com/

AUTHORS and MAINTAINERS
       This module is currently maintained by

	   H.Merijn Brand <h.m.brand@xs4all.nl>

       in close cooperation with and help from

	   Jens Rehsack <sno@NetBSD.org>

       The original author is Jochen Wiedmann.	Previous maintainer was Jeff
       Zucker

COPYRIGHT AND LICENSE
       Copyright (C) 2009-2010 by H.Merijn Brand Copyright (C) 2004-2009 by
       Jeff Zucker Copyright (C) 1998-2004 by Jochen Wiedmann

       All rights reserved.

       You may distribute this module under the terms of either the GNU
       General Public License or the Artistic License, as specified in the
       Perl README file.

perl v5.14.1			  2010-09-16			   DBD::CSV(3)
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