DBD::CSV - DBI driver for CSV files
use DBI;
# See "Creating database handle" below
$dbh = DBI->connect ("dbi:CSV:", undef, undef, {
f_ext => ".csv/r",
RaiseError => 1,
}) or die "Cannot connect: $DBI::errstr";
# Simple statements
$dbh->do ("CREATE TABLE foo (id INTEGER, name CHAR (10))");
# Selecting
my $sth = $dbh->prepare ("select * from foo");
$sth->execute;
$sth->bind_columns (\my ($id, $name));
while ($sth->fetch) {
print "id: $id, name: $name\n";
}
# Updates
my $sth = $dbh->prepare ("UPDATE foo SET name = ? WHERE id = ?");
$sth->execute ("DBI rocks!", 1);
$sth->finish;
$dbh->disconnect;
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, the SQL::Statement manpage for details on
SQL::Statement and the DBD::File manpage for details on the base class DBD::File.
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
X
-
A recent version of the DBI (Database independent interface for Perl).
See below why.
- DBD::File
X
-
This is the base class for DBD::CSV, and it is part of the DBI
distribution. As DBD::CSV requires a matching version of the DBD::File manpage
which is (partly) developed by the same team that maintains
DBD::CSV. See META.json or Makefile.PL for the minimum versions.
- SQL::Statement
X
-
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 the DBI::SQL::Nano manpage for more details. Note
that the test suite does only test in this mode in the development
environment.
- Text::CSV_XS
X
-
This module is used to read and write rows in a CSV file.
Installing this module (and the prerequisites from above) is quite simple.
The simplest way is to install the bundle:
$ cpan Bundle::DBD::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-0.40.tgz | tar xf -
(this is for Unix users, Windows users would prefer WinZip or something
similar) and then enter the following:
cd DBD-CSV-0.40
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. the ExtUtils::MakeMaker manpage.
All SQL processing for DBD::CSV is done by SQL::Statement. See
the SQL::Statement manpage for more specific information about its feature set.
Features include joins, aliases, built-in and user-defined functions,
and more. See the SQL::Statement::Syntax manpage for a description of the SQL
syntax supported in DBD::CSV.
Table- and column-names are case insensitive unless quoted. Column names
will be sanitized unless raw_header is true.
For most things, DBD-CSV operates the same as any DBI driver.
See DBI for detailed usage.
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_dir_search => [],
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_bom => 0,
csv_tables => {
syspwd => {
sep_char => ":",
quote_char => undef,
escape_char => undef,
file => "/etc/passwd",
col_names => [qw( login password
uid gid realname
directory shell )],
},
},
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 specifying entries in the attribute hash is easier to read and to
maintain.
The default value for csv_binary is 1 (True).
The default value for csv_auto_diag is <1>. Note that this might cause
trouble on perl versions older than 5.8.9, so up to and including perl
version 5.8.8 it might be required to use ;csv_auto_diag=0 inside the
DSN or csv_auto_diag = 0> inside the attributes.
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.
The following examples insert some data in a table and fetch it back:
First, an example where the column data is concatenated in the SQL 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 quote column data passed as parameters.
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 used and will be
passed to the prepare method as the 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 the SQL::Statement manpage 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");
In the above examples we have never cared about return codes. Of
course, this is not 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.
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
X
-
Always on
- ChopBlanks
X
-
Works
- NUM_OF_FIELDS
X
-
Valid after
$sth->execute
- NUM_OF_PARAMS
X
-
Valid after
$sth->prepare
- NAME
X
-
- NAME_lc
X
-
- NAME_uc
X
-
Valid after
$sth->execute; undef for Non-Select statements.
- NULLABLE
X
-
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
In addition to the DBI attributes, you can use the following dbh
attributes:
- f_dir
X
-
This attribute is used for setting the directory where CSV files are
opened. Usually you set it in the dbh and it defaults to the current
directory (``.''). However, it may be overridden in statement handles.
- f_dir_search
X
-
This attribute optionally defines a list of extra directories to search
when opening existing tables. It should be an anonymous list or an array
reference listing all folders where tables could be found.
my $dbh = DBI->connect ("dbi:CSV:", "", "", {
f_dir => "data",
f_dir_search => [ "ref/data", "ref/old" ],
f_ext => ".csv/r",
}) or die $DBI::errstr;
- f_ext
X
-
This attribute is used for setting the file extension.
- f_schema
X
-
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
X
-
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 column basis, but DBD::File
now allows the encoding to be set on the underlying file. If this attribute is
not set, or undef is passed, the file will be seen as binary.
- f_lock
X
-
With this attribute you can specify a locking mode to be used (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:
- X<0>
Force no locking at all.
- X<1>
Only shared locks will be used.
- X<2>
Only exclusive locks will be used.
But see KNOWN BUGS in the DBD::File manpage.
- csv_class
-
The attribute csv_class controls the CSV parsing engine. This defaults
to
Text::CSV_XS, but Text::CSV can be used in some cases, too.
Please be aware that Text::CSV does not care about any edge case as
Text::CSV_XS does and that Text::CSV is probably about 100 times
slower than Text::CSV_XS.
In order to use the specified class other than Text::CSV_XS, it needs
to be loaded before use. DBD::CSV does not require/use the
specified class itself.
- csv_eol
X
-
- csv_sep_char
X
-
- csv_quote_char
X
-
- csv_escape_char
X
-
- csv_csv
X
-
The attributes csv_eol, csv_sep_char, csv_quote_char and
csv_escape_char are corresponding to the respective attributes of the
csv_class (usually Text::CSV_CS) object. You may 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
X
-
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_bom
X
-
With this option set, the CSV parser will try to detect BOM (Byte Order Mark)
in the header line. This requires the Text::CSV_XS manpage version 1.22 or higher.
$dbh = DBI->connect ("dbi:CSV:", "", "", { csv_bom => 1 });
$dbh->{csv_bom} = 1;
- csv_tables
X
-
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:
- o
-
All valid attributes to the CSV parsing module. Any of them can optionally
be prefixed with
csv_.
- oo
-
All attributes valid to DBD::File
If you pass it f_file or its alias file, f_ext has no effect, but
f_dir and f_encoding still have.
csv_tables => {
syspwd => { # Table name
csv_sep_char => ":", # Text::CSV_XS
quote_char => undef, # Text::CSV_XS
escape_char => undef, # Text::CSV_XS
f_dir => "/etc", # DBD::File
f_file => "passwd", # DBD::File
col_names => # DBD::File
[qw( login password uid gid realname directory shell )],
},
},
- csv_*
X
-
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 only likely to be useful for reading (select)
handles. Examples:
$dbh->{csv_allow_whitespace} = 1;
$dbh->{csv_allow_loose_quotes} = 1;
$dbh->{csv_allow_loose_escapes} = 1;
See the Text::CSV_XS documentation for the full list and the documentation.
- f_file
X
-
The name of the file used for the table; defaults to
"$dbh->{f_dir}/$table"
- eol
X
-
- sep_char
X
-
- quote_char
X
-
- escape_char
X
-
- class
X
-
- csv
X
-
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 basis.
- col_names
X
-
- skip_first_row
X
-
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, ...
Note that column names that match reserved SQL words will cause unwanted
and sometimes confusing errors. If your CSV has headers that match reserved
words, you will require these two attributes.
If test.csv looks like
select,from
1,2
the select query would result in select select, from from test;, which
obviously is illegal SQL.
- raw_header
X
-
Due to the SQL standard, field names cannot contain special characters
like a dot (
.) or a space ( ) unless the column names are quoted.
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 and the entries in the first line of the CSV data will be
used verbatim for column headers and field names. 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.
Currently, the sanitizing of headers is as simple as
s/\W/_/g;
Note that headers (column names) might be folded in other parts of the code
stack, specifically SQL::Statement, whose docs mention:
Wildcards are expanded to lower cased identifiers. This might
confuse some people, but it was easier to implement.
That means that in
my $sth = $dbh->prepare ("select * from foo");
$sth->execute;
while (my $row = $sth->fetchrow_hashref) {
say for keys %$row;
}
all keys will show as all lower case, regardless of the original header.
It's strongly recommended to check the attributes supported by
Metadata in the DBD::File manpage.
Example: Suppose 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
override them on a per table basis:
require DBI;
my $dbh = DBI->connect ("dbi:CSV:");
$dbh->{csv_tables}{passwd} = {
eol => "\n",
sep_char => ":",
quote_char => undef,
escape_char => undef,
f_file => "/etc/passwd",
col_names => [qw( login password uid gid
realname directory shell )],
};
$sth = $dbh->prepare ("SELECT * FROM passwd");
These methods are inherited from DBD::File:
- data_sources
X
-
The
data_sources method returns a list of sub-directories of the current
directory in the form ``dbi:CSV:directory=$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
X
-
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.
-
The module is using flock () internally. However, this function is not
available on some platforms. Use of 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).
- Tests
X
-
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 $_") for DBI-tables ();
- errors Make sure that all documented exceptions are tested.
. write to write-protected file
. read from badly formatted csv
. pass bad arguments to csv parser while fetching
Add tests that specifically test DBD::File functionality where
that is useful.
- RT
X
-
Attack all open DBD::CSV bugs in RT
- CPAN::Forum
X
-
Attack all items in http://www.cpanforum.com/dist/DBD-CSV
- Documentation
X
-
Expand on error-handling, and document all possible errors.
Use Text::CSV_XS::error_diag () wherever possible.
- Debugging
X
-
Implement and document dbd_verbose.
- Data dictionary
X
-
Investigate the possibility to store the data dictionary in a file like
.sys$columns that can store the field attributes (type, key, nullable).
- Examples
X
-
Make more real-life examples from the docs in examples/
DBI, the Text::CSV_XS manpage, the SQL::Statement manpage, the DBI::SQL::Nano manpage
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/
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 (C) 2009-2021 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.
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