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CSV Database Validation

by Ovid (Cardinal)
on Nov 19, 2001 at 09:20 UTC ( [id://126212]=sourcecode: print w/replies, xml ) Need Help??
Category: Utility Scripts
Author/Contact Info



Recently, for a personal project, I was using DBD::CSV to create a simple database. I was dismayed how little validation there was. The following program will allow you to create a CSV database and validate unique fields, foreign key constraints, and simple data types. You can also use this to validate data against regular expressions. Naturally, these are one-time validations.

Also included is support for validating an existing CSV database or CSV file. See POD for complete details.

Please let me know if you find any bugs in this code. Also, a code review would be appreciated :)

#!/usr/bin/perl -w
use strict;
use DBI;
use Text::CSV_XS;
use Getopt::Std;

use vars qw/ %option /;

getopts( 's:d:r:vnh', \%option );

if ( $option{ h } ) {

foreach ( qw/ s r d / ) {
    die &usage if ! $option{ $_ };

my $schema_file = $option{ s };
my $raw_data    = $option{ r };
my $data_dir    = format_data_dir( $option{ d } );
my $no_header   = $option{ n } || 0;

# errors that are not immediately fatal will be written to the followi
+ng log:
my $error_log  = 'err.log';

if ( ! -e $data_dir ) {
    if ( $option{ v } ) {
        # we're validating an exisisting database, so there had
        # darned well better be one there!
        die "Attempt to validate database '$data_dir' failed.  Folder 
+does not exist.\n";
    mkdir $data_dir or die "Could not mkdir $data_dir: $!";

my $database = schema( $schema_file );

if ( $option{ v } ) {
    print "\nWarning: you are about to validate an existing database.\
+n" .
          "This program will drop the tables prior to validation.\n" .
          "Did you back up the database? ";
    exit if 'y' ne lc substr <STDIN>, 0, 1;

    create_raw_data( $data_dir, $raw_data, $no_header, $database );

my $dbh = DBI->connect("DBI:CSV:f_dir=$data_dir", { RaiseError => 1 } 
create_database( $dbh, $data_dir, $database );

print "All tables successfully created.\n";

add_data_to_database( $dbh, $raw_data, $database );

print "All data successfully added to database.\n";

open ERROR_LOG, "> $error_log" or die "Cannot open $error_log for writ
+ing: $!";
print "Now validating unique fields.\n";
my $error_count = validate_unique_fields( \*ERROR_LOG, $dbh, $database
+ );

print "Now validating foreign key constraints.\n";
$error_count += validate_foreign_keys( \*ERROR_LOG, $dbh, $database );

print "Now validating data against regular expressions.\n";
$error_count += validate_with_regexes( \*ERROR_LOG, $dbh, $database );

close ERROR_LOG;

if ( $error_count ) {
    my $text = $error_count == 1 ? " was" : "s were";
    print "\nWARNING\n$error_count error$text found while validating t
+he data.  Errors were written to '$error_log'\n";
} else {
    unlink $error_log;
    print "\nNo errors were found while validating the data.\n";

###                ###
#  main subs follow  #
###                ###

sub schema {
    # The following datatypes are used for documentation purposes, but
    # DBD::CSV does not support these properties.  They are mainly her
+e so
    # that programmers can customize these attributes for their own da
    # They will also be used in this program to ensure that data added
+ to database
    # will pass validation (this will minimize database corruption )
    # currently, each key in %data_type points to a hashref.  This is 
+done in case
    # we need to add extra functionality in the future.
    # note that DBD::CSV relies on SQL::Statement which does not suppo
+rt most
    # data types, such as DateTime or Boolean.

    my $schema_file = shift;

    my %data_type = (
        INT => {
            validate => \&is_int
        VARCHAR => {
            validate => \&is_varchar
        CHAR => {
            validate => \&is_char

    open SCHEMA, "< $schema_file" or die "Cannot open $schema_file for
+ reading:$!\n";

    my $table = '';
    my %schema;
    while ( <SCHEMA> ) {
        next if /^#/;    # skip comments;
        next if /^\s*$/; # skip blank lines
        $table = $1, next if ( /^\s*\[([^\]]+)\]\s*$/ );

        if ( substr( $_, 0, 1 ) ne '_' ) {
            if ( ! $table ) {
                error_in_data( 'unknown', $_, "Could not determine tab
+le for line $. in schema '$schema_file'");
            my ( $field, $type, @extra ) = split;
            $type = uc $type;
            $type = 'INT' if $type eq 'INTEGER';
            if ( $type !~ /^(INT|(?:VAR)?CHAR)/ ) {
                error_in_data( $table, $_, "Unknown type '$1' in schem
+a '$schema_file'" );

            if ( ! exists $schema{ $table }{ $field } ) {
                $schema{ $table }{ $field } = $type;
                push @{ $schema{ $table }{ _field_order } }, $field; #
+ holds the order of fields

                if ( defined $extra[0] and uc $extra[0] eq 'UNIQUE' ) 
                    push @{ $schema{ $table }{ _unique } }, $field; # 
+field must not have duplicates
            if ( defined $extra[-1] and $extra[-1] =~ m!^/(.*)/$! ) {
            $schema{ $table }{ _regex }{ $field } = $1;
            } else {
                error_in_data( $table, $_, "Redefined field '$field' i
+n schema '$schema_file'" );
        } elsif ( substr( $_, 0, 12 ) eq '_foreign_key' ) {
            my ( undef, @data ) = split;
            if ( @data != 3 ) {
                error_in_data( $table, $_, "Foreign key definitions ar
+e in form 'thistable.field, foreign.table, foreign.table.field");
            } else {
                push @{ $schema{ $table }{ _foreign_key } }, \@data;
    close SCHEMA;

    foreach my $table ( keys %schema ) {
        $schema{ $table }{ _rec_count } = 0; # stop uninitialized warn
+ings later
    $schema{ _data_type } = \%data_type;
    return \%schema;

sub create_raw_data {
    # This will only be called if validating an existing database
    # or CSV file
    my ( $data_dir, $raw_data, $no_header, $database ) = @_;
    if ( -e $raw_data ) {
        print "Warning: raw data file '$raw_data' exists.  Overwrite? 
+[y/n] ";
        exit if 'y' ne lc substr <STDIN>, 0, 1;

    open RAW_DATA, "> $raw_data" or die "Cannot open $raw_data for wri
+ting: $!";
    foreach my $table ( keys %$database ) {
        next if '_' eq substr $table, 0, 1; # these are data keys
        my $fields = join ', ', @{ $database->{ $table }{ _field_order
+ } };
        $fields = "# $fields\n";
        open TABLE, "< $data_dir$table" or die "Cannot open $data_dir$
+table for reading: $!";
        my $header = <TABLE>;

        if ( ! $no_header ) {
            $header = '';
        print RAW_DATA "table=$table\n", $fields, $header, <TABLE>, "\
        close TABLE;
    close RAW_DATA;

sub create_database {
    # drop tables if they exist and then recreate them.
    my ( $dbh, $data_dir, $database ) = @_;
    foreach my $table ( keys %$database ) {
        next if substr( $table, 0, 1 ) eq '_';
        if ( -e $data_dir.$table ) {
            $dbh->do( "DROP TABLE $table" );
        my @fields;
        if ( ! exists $database->{$table}{_field_order} ) {
            die "Table: '$table' does not have a _field_order specific
        my @field_order = @{ $database->{$table}{_field_order} };
        my $order_count = unique( @field_order );
        if ( @field_order != $order_count ) {
            die "Table: '$table' has duplicate fields in _field_order.
        my $field_count = unique( grep { /^[^_]/ } keys %{$database->{
+ $table }} );
        if ( $field_count != $order_count ) {
            my $comp = $field_count > $order_count ? "more" : "fewer";
            die "Table '$table' has $comp fields than _field_order spe

        foreach my $field ( @field_order ) {
            if ( ! exists $database->{ $table }{ $field } ) {
                die "Table: '$table' does not have field '$field' list
+ed in _field_order";
            push @fields, "$field $database->{$table}{$field}";
        my $fields = join ',', @fields;
        $dbh->do("CREATE TABLE $table ( $fields )");

sub add_data_to_database {
    # This could use some work.  Just a roungh hack to get the data.
    # for right now it's fine, but in the future, this could be
    # problematic if someone creates a huge amount of data.
    # Records are separated by putting a period on a line by itself: "
    # First line of each record is table name.  Subsequent records are
+ fields
    # to be entered.  Empty lines and lines beginning with a # are ski

    my ( $dbh, $raw_data, $database ) = @_;

    my $csv = Text::CSV_XS->new;
    local $/ = "\n.\n";
    open DATA_FILE, "< $raw_data" or die "Cannot open $raw_data for re
+ading: $!\n";
    while ( <DATA_FILE> ) {
        next if /^\s*$/;
        my @records = grep { /^[^#]/ } split /\n/;
        my $table = trim( shift @records );
        if ( $table =~ /=/ ) {
            $table = trim( ( split /=/, $table, 2 )[-1] );

        if ( ! exists $database->{$table} ) {
            die "Table '$table' found in input data but is not in sche

        my $place_holders = '?,' x @{ $database->{$table}{_field_order
+} };
        chop $place_holders; # remove trailing comma
        my $sql = "INSERT INTO $table VALUES ( $place_holders )";
        my $sth = $dbh->prepare( $sql );
        foreach my $record ( @records ) {
            next if $record !~ /\S/ or $record =~ /^\.$/; # skip empty
+ records
            my $status;
            if( ! ( $status = $csv->parse($record) ) ) { # parse a CSV
+ string into fields
                error_in_data( $table, $record, "Bad argument in CSV r
+ecord" );
            my @columns = $csv->fields();      # get the parsed fields
            if ( @columns != @{ $database->{$table}{_field_order} } ) 
                my $in_length = @columns;
                my $expected_length = @{ $database->{$table}{_field_or
+der} };
                error_in_data( $table, $record, "Expected $expected_le
+ngth columns.  Found $in_length columns." );
            } else {
                validate_record( $database, $table, \@columns, $csv );
                $sth->execute( @columns );
                $database->{ $table }{ _rec_count }++;
        } # next record
    } # end while
    close DATA_FILE;
    print "\n";
    foreach my $table ( sort keys %$database ) {
        next if substr( $table, 0, 1 ) eq '_';
        my $count = $database->{ $table }{ _rec_count };
        if ( $count == 0 ) {
            print "WARNING: table '$table' created but no records adde
        } else {
            print "$count records added to table '$table'.\n";
    print "\n";

sub validate_unique_fields {
    # for each defined unique field, grab all of them from the
    # database and add them to an autoincrementing hash.  If any
    # value is greater than one, then we know we have more than
    # one unique key
    my ( $err, $dbh, $database ) = @_;
    my $error_count = 0;
    foreach my $table ( %$database ) {
        if ( exists $database->{ $table }{ _unique } ) {
            my @unique_fields = @{ $database->{ $table }{ _unique } };
            foreach my $field ( @unique_fields ) {
                my %field_count;
                my $sql = "SELECT $field FROM $table";
                my $fields = $dbh->selectall_arrayref( $sql );
                foreach ( @$fields ) {
                    $field_count{ $_->[0] }++;
                foreach ( keys %field_count ) {
                    if ( $field_count{$_} > 1 ) {
                        print $err "Table: '$table' Unique field: '$_'
+ was found $field_count{$_} times\n";
            } # next $field
    } # next $table
    return $error_count;

sub validate_foreign_keys {
    # the foreign keys for a table are an array ref of array refs.
    # each inner array ref is a table key, foreign table, and foreign 
    # this routine grabs the table keys and ensures that each one matc
    # a foreign key in the foreign table.
    my ( $err, $dbh, $database ) = @_;
    my $error_count = 0;
    foreach my $table ( %$database ) {
        my $last_error_count = $error_count;
        if ( exists $database->{ $table }{ _foreign_key } ) {

            my @fkey_array = @{ $database->{ $table }{ _foreign_key } 
            my $base_err = 'Foreign Key constraint violated.';

            foreach my $fkey_data ( @fkey_array ) {
                my ( $this_key, $ftable, $ftable_key ) = @$fkey_data;
                if ( ! exists $database->{ $table }{ $this_key } ) {
                    my $err_message = "$base_err  Table '$table' does 
+not have field '$this_key'\n";
                    print $err $err_message;
                if ( ! exists $database->{ $ftable } ) {
                    my $err_message = "$base_err  Foreign table '$ftab
+le' does not exist.\n";
                    print $err $err_message;
                if ( exists $database->{ $ftable } and ! exists $datab
+ase->{ $ftable }{ $ftable_key } ) {
                    my $err_message = "$base_err  Foreign table '$ftab
+le' does not have field '$ftable_key\n";
                    print $err $err_message;
                if ( exists $database->{ $ftable }
                     exists $database->{ $ftable }{ $ftable_key }
                     ( ! exists $database->{ $ftable }{ _unique }
                       ! grep { /$ftable_key/ } @{$database->{ $ftable
+ }{ _unique }}
                    my $err_message = "$base_err  Table '$table', fiel
+d '$this_key'. ".
                                      "'$ftable_key' not defined as UN
+IQUE in '$ftable'\n";
                    print $err $err_message;
                next if $error_count > $last_error_count;
                my $sql = "SELECT $this_key FROM $table";
                my $sth = $dbh->prepare( $sql );
                my $tbl_array_ref = $sth->fetchall_arrayref;
                foreach ( @$tbl_array_ref ) {
                    my $data = $dbh->quote( $_->[ 0 ] );
                    my $sql  = "SELECT $ftable_key FROM $ftable WHERE 
+$ftable_key = $data";
                    my $sth  = $dbh->prepare( $sql );
                    my $rv   = $sth->execute;
                    if ( $rv eq '0E0' ) {
                        my $err_message = "$base_err  Table '$table', 
+field '$this_key', ".
                                          "value $data Not found in ta
+ble '$ftable', field '$ftable_key'\n";
                        print $err $err_message;
            } # next $fkey_data
    } # next $table
    return $error_count;

sub validate_record {
    # this function loops through each field in the record, determines
    # the type of field and then attempts to verify that the data in t
    # field does, in fact, match the data type supplied.
    # The program will die if the data type does not match
    my ( $database, $table, $columns, $csv ) = @_;
    my $data_type = $database->{ _data_type };
    my @fields = @{ $database->{$table}{_field_order} };
    foreach my $index ( 0 .. $#fields ) {
        my ( $type ) = ( $database->{ $table}{ $fields[ $index] } =~ /
+^(\w+)/ );
        my $function = $data_type->{ $type }{ 'validate' };
        if ( ref $function ne 'CODE' ) {
            # this should not happen
            die "No validation routine found for type: '$type'.";
        my $type_match = $function->( $columns->[$index], $database->{
+ $table }{ $fields[$index] } );
        if ( ! $type_match ) {
            my $status = $csv->combine( @$columns );
            my $data   = $csv->string;
            my $err_message = "Field: '$columns->[ $index ]' does not 
+match data type: '$database->{ $table }{ $fields[$index] }'.";
            error_in_data( $table, $data, $err_message );

sub validate_with_regexes {
    # every field in the database may have an optional regex added to
    # describe valid data types.  This sub will test whether or not th
    # data for those fields matches the regex.
    my ( $err, $dbh, $database ) = @_;
    my $error_count = 0;
    foreach my $table ( %$database ) {
        if ( exists $database->{ $table }{ _regex } ) {
            my %fields = %{$database->{ $table }{ _regex }};
            my @bad_regexes;
            while ( my ( $field, $regex ) = each %fields ) {
                if ( ! is_valid_pattern( $regex ) ) {
                    print $err "Table: '$table', field '$field' had in
+valid pattern '$regex'. Discarded.\n";
                    push @bad_regexes, $field;
            delete @fields{ @bad_regexes } if @bad_regexes;
            my $fieldnames = join ',', keys %fields;
            my $sql = "SELECT $fieldnames FROM $table";

            my $sth = $dbh->prepare( $sql );
            while ( my $data = $sth->fetchrow_hashref ) {
                foreach ( keys %$data ) {
                    my $value = $data->{ $_ };
                    my $regex = $fields{ $_ };
                    if ( $value !~ /$regex/ ) {
                        print $err "Table: '$table' field: '$_' value:
+ '$value' did not match /$fields{$_}/.\n";
    } # next $table
    return $error_count;

###                   ###
#  utility subs follow  #
###                   ###

sub usage {
    print <<"    END_USAGE";

usage: [-h] [-s schema_file] [-d database_dir] [-r raw_
                      [-v] [-n]
Validate and/or create a CSV database.
-h              help
-?              help
-s schema_file  File containing schema.  See POD for details
-d database_dir The directory where the database will be created.  If 
+-v is
                supplied, this is location where data is to be read fr
+om, and
                then written back to.
-r raw_data     The file containing raw database information.  If -v i
                supplied, this is where the raw information will be wr
+itten to.
-v              Validate existing database.
-n              If -v is used, this says that the data in -d does *not
+* have a
                header line labeling the fields.

sub error_in_data {
    my ( $table, $record, $message ) = @_;
    die "\nERROR in table: '$table'\n$message\nRecord: $record\n";

sub trim {
    my $data = shift;
    $data =~ s/^\s+//;
    $data =~ s/\s+$//;

sub unique {
    my @array = @_;
    my %count;
    @array = grep { ! $count{$_}++ } @array;

# each routine returns a true/false value for whether or not the data 
+passes validation
sub is_int {
    my $data = shift;
    return $data =~ /^-?\d+$/ ? 1 : 0;

sub is_varchar {
    my ( $data, $desc ) = @_;
    # $desc will typically be something like VARCHAR(64)
    my ( $length ) = ( $desc =~ /\(\s*(\d+)/ );
    return ( length $data <= $length ) ? 1 : 0;

sub is_char {
    my ( $data, $desc ) = @_;
    # $desc will typically be something like CHAR(8)
    my ( $length ) = ( $desc =~ /\(\s*(\d+)/ );
    return ( length $data == $length ) ? 1 : 0;

sub is_valid_pattern {
    my $pattern = shift;
    return eval { '' =~ /$pattern/; 1 } || 0;

sub format_data_dir {
    my $dir = shift;
    # the following is stolen from
    my $os = $^O;
    unless ( defined $os and $os ) {
        require Config;
        $os = $Config::Config{'osname'};
    my $sep;
    if ($os=~/Win/i) {
        $sep = '\\';
    } elsif ($os=~/vms/i) {
        $sep = '/';
    } elsif ($os=~/bsdos/i) {
        $sep = '/';
    } elsif ($os=~/dos/i) {
        $sep = '\\';
    } elsif ($os=~/^MacOS$/i) {
        $sep = ':';
    } elsif ($os=~/os2/i) {
        $sep = '\\';
    } else {
        $sep = '/';
    $dir .= $sep if $dir !~ /$sep$/; # add the separator if it's not t
    return $dir;


=head1 NAME - Simple validation for DBD::CSV database creation


 perl -s schema.txt -r raw_data.txt -d data_dir


DBD::CSV is a useful module if you are forced to work with CSV files a
+s a
database.  Unfortunately, the module does no data validation.  This
program allows you to define a schema, along with UNIQUE fields and fo
key constraints.  Further, basic data type validation for INT, CHAR, a
VARCHAR is supported.  Oddly enough, DBD::CSV, while only allowing tho
datatypes to be used in a C<CREATE table> statement, does not actually
+ check
to see whether or not the data you are inserting matches those datatyp

If one supplies the -v option on the command line, then this program v
and existing database.  The -r option is then used to specify where th
raw_data will be written to.  The -n ("no header") option may be used 
validating if you are validating a CSV file while does not have field 
listed as the first line of the file.

Much of the information provided in here is for those who wish to main
+tain and
extend this program.  These sections are marked with B<MAINTENANCE BEG
+IN> and
B<MAINTENANCE END> and may be skipped if you do not care about this.

=head1 Schema

Each database to be created and validated must have an associated sche
created by the programmer.

The schema location is passed to the program via the command line -s s
The schema is then read into the C<$schema> variable in C<&schema>. C<
is a hash ref.  Every key in the hash that does not begin with an unde
(_) is assumed to be a table name.  Each table is also a hashref.  Eve
+ry key
in a table hash that does not begin with an underscore is assumed to b
+e a
field name.  Keys beginning with underscores are metadata describing t
respectives tables.  These keys are C<_field_order>, C<_foreign_key>,
C<_unique>, and C<_rec_count>.  These are used to validate the data in
+ the

The format of the schema file must be as follows (items enclosed in cu
braces are optional):

 field DATATYPE {UNIQUE} {/regex/}
 _foreign_key tablename.field foreigntable foreigntable.key

Currently, the only datatypes supported are INT, CHAR, and VARCHAR.  C
+HAR and
VARCHAR must have a number in parenthese following them which specifie
+s the
maximum number of characters allowed.  For example:

 user_id   INT UNIQUE
 user_name VARCHAR(10)

In the schema, blank lines and lines starting with a sharp (#) are ski
Fields in the database will be in the order listed.  As soon as a new 
name is encountered, the previous table definition is assumed to be co

A regex may be supplied as the last item on the field definition line.
+  If a
field value does not match the regex, a warning will be written to the
+ error
log.  For example to ensure that user ids are positive integers:

 user_id INT UNIQUE /^\d+$/

The regex B<must> begin and end with a forward slash.  You can use a r
+egex such
as C</.+/> to enforce a C<NOT NULL> requirement.

Also note that you may write C<INTEGER> instead of C<INT>, if you pref

=head2 Table Fields

Each field in a table may be of type INT, VARCHAR, or CHAR.  These are
+ the only
datatypes supported by DBD::CSV when creating tables.  These datatypes
+ are
stored in C<$int>, C<$varchar>, and C<$char>, respectively.  Let's exa
+mine the
following SQL C<CREATE> statement and see how it's translated:

    user_id INTEGER UNIQUE,
    name    VARCHAR(64),
    area    CHAR(8)


The following is the minimum legal specification for this table, as de
+fined in
the C<$schema> variable.

 users => {
     user_id      => $int,
     name         => "$varchar(64)",
     area         => "$char(8)",
     _field_order => [qw/ user_id name area /]

Upon validating the data, and exception will be thrown if C<user_id> d
+oes not
match the regular expression C</^-?\d+$/>.

The C<name> would throw an exception if it exceeded the length of 64 a
C<area> would throw an exception if the length did not match 8.  When 
+the table
is created, the order of fields in the table would match the order spe
+cified in


This definition for this table would be created in the schema file as 

 user_id INT
 name    VARCHAR(64)
 area    CHAR(8)


=head2 Metadata

As mentioned previously, there are four metadata keys used for tables.
+  These
are C<_field_order>, C<_foreign_key>, C<_unique>, and C<_rec_count>.

=over 4

=item _field_order


Since hashes have an effectively arbitrary order for their keys, the
C<_field_order> key is used to specify the order of the fields when th
+e tables
are created in the database.  This is an array reference in the C<$sch

 _field_order => [qw/ user_id name area /]

If the tables fields and the field order do not match, an exception wi
+ll be
thrown when the program attempts to create the table.


=item _unique

C<DBD::CSV> does not actually allow for PRIMARY KEYS.  Rather than try
+ to write
a bunch of arcane and effectively useless code to allow for this, we h
+ave a
C<UNIQUE> specifier.  Internally, this is merely an array reference sp
the keys in the table for which we do not allow duplicate values.


In the example of the C<users> table above, the table specification is
+ as

 users => {
     user_id      => $int,
     name         => "$varchar(64)",
     area         => "$char(8)",
     _field_order => [qw/ user_id name area /],
     _unique      => [qw/ user_id /]


To make a user_id UNIQUE, we do the following:

 user_id INT UNIQUE
 name    VARCHAR(64)
 area    CHAR(8)

After all data has been added to the database, the program will valida
+te all
unique fields and an error will be written to an error log if any dupl
values are found in these fields.

=item _foreign_key

Despite arguments by some diehard MySQL supporters :), any real databa
supports foreign key constraints.  Naturally, DBD::CSV does not.  The
C<_foreign_key> value for a table is an array ref of array refs.  Each
+ inner
array has the following format:

 field foreign_table foreign_field

After data is added to the database, foreign key validation will occur
+.  For
each table that has a C<_foreign_field> key, the program will look up 
+the value
in C<field> and ensure that C<foreign_table> has a corresponding valud
+ in
C<foreign_field>.  Further, the C<foreign_field> must be designated as
+ a
C<_unique> field.  If these conditions are not met, an entry will be a
+dded to
the error log.

Consider a lookup table for a music CD database.  Each CD could potent
have several artists and each artist could be present on several CDs. 
+ Assuming
we have two tables named C<artists> and C<CDs>, with C<artist_id> and 
respectively, we could define the lookup table as follows:


Internal representation

 cd_artist => {
     artist       => $int,
     cd           => $int,
     _field_order => [qw/ artist_id cd_id /],
     _foreign_key =>    [
         [ qw/ artist artists artist_id / ],
         [ qw/ cd CDs CD_id / ]


 artist INT
 cd     INT
 _foreign_key artist artists artist_id
 _foreign_key cd CDs CD_id

Note that the tables will still be created if a foreign key constraint
+ is
violated and there is nothing in the C<DBD::CSV> module to prevent thi
+s.  This
is for advisory purposes only.  Your database will function even if th
+e foreign
key is not defined as C<UNIQUE>, but you should probably take a look a
+t your
schema to look for problems.

=item _record_count

This is an internal field used to track how many records were written 
+for each
table.  After data is added to the database, a list of the number of r
written to each table will be displayed to the screen.  A B<WARNING> m
will occur for all tables that have no records written.



=head2 Creating a schema

Let's take a look at a simple database and see how it's all put togeth
+er. We
have three tables: CDs, artist, and cd_artist.  The last is a lookup t
What follows is not intended to be an complete database.

 CD_id         INT /^\d++$/
 CD_name       VARCHAR(30) /.+/
 # date will be in YYYY
 year_released CHAR(4)

 artist_id     INT UNIQUE /^\d+$/
 artist_name   VARCHAR(30) /.+/

 artist        INT
 cd            INT
 _foreign_key artist artist artist_id
 _foreign_key cd CDs CD_id

Note that when this schema is read that the lines are split on whitesp
C<DBD::CSV> does not allow whitespace in a table name.

Further, I would not recommend the naming convention that I have used.
+  Foreign
key field names should (IMHO) match the field names of the tables that
+ they
should match.  I have made them distinct so that it's easier to distin
them in this example.

=head2 Creating the raw data for the database

Now that we have our schema, we need to create the raw data.  The data
+ file
contains all of the tables and data that will be added to the database
+.  Each
table is separated by "\n.\n".  The data for a table will be read in c
that is split on the separator.  I suppose that it's possible for some
+one to
have such a large amount of data that this could be a problem, but if 
+you do,
you should be using a real database.  As with the schema file, lines c
of all white space or beginning with a sharp will be discarded.  Field
+s must be
separated with a comma and if a field contains a comma, it must be quo

As each chunk is read, the program looks for the first line which cont
+ains data
and assumes this to be a table name.  You may use either of the two fo
statements to declare a tablename:


or simply:


Here is a small raw data file:

 #artist_id, artist_name

 # CD_id, CD_name,date_released
 1,One Second,1987
 3,"Ovid's Greatest Hits, Volume Zero",0000

 # artist, cd

Let's say we save the schema in a file called C<schema.txt> and the da
+ta in
a file called C<raw.txt> and we want to write this to a database calle
C<stuff>.  We'd use the following command:

 perl -s schema.txt -r raw.txt -d stuff

If a directory called C<stuff> does not exist, it will be created for 
Issuing that command, we get the following:

 All tables successfully created.

 ERROR in table: 'CDs'
 Field: 'Ovid's Greatest Hits, Volume Zero' does not match data type: 
 Record: 3,"Ovid's Greatest Hits, Volume Zero",0000

Be examing our schema, we see that we have defined C<CD_name> as C<VAR
The field in question is over 30 characters long, so we change C<CD_na
+me> in
the schema to C<VARCHAR(40)>.  Then we rerun the command.  We get the 

 All tables successfully created.

 3 records added to table 'CDs'.
 2 records added to table 'artist'.
 3 records added to table 'cd_artist'.

 All data successfully added to database.
 Now validating unique fields.
 Now validating foreign key constraints.
 Now validating data against regular expressions.

 3 errors were found while validating the data.  Errors were written t
+o 'err.log'

Hmm... what errors?  Opening the error.log, we see:

 Foreign Key constraint violated.  Table 'cd_artist', field 'artist', 
+value '4' Not found in table 'artist', field 'artist_id'
 Foreign Key constraint violated.  Table 'cd_artist', field 'cd'. 'CD_
+id' not defined as UNIQUE in 'CDs'
 Table: 'CDs', field 'CD_id' had invalid pattern '^\d++$'. Discarded.

Oops.  Let's change those in our schema.

 CD_id         INT UNIQUE /^\d+$/

The regular expression, in this case, may seem superfluous, but it doe
+s two things for us:

 1.  It effectively ensures that we will have at least one digit in th
+e id.
 2.  It ensures that all ids are positive.

Also, we see that there is no artist with an id of 4.  That should be 
+changed to 2.
Rerunning the program this time creates all of the tables and generate
+s absolutely
no errors.

=head1 Validating an existing database

If you have an existing CSV database, define a schema for the database
+.  Then,
run the program as normal using the C<-v> switch.  This tells the prog
+ram that
we will be validating an existing database rather than creating a new 
+one from
scratch.  If you wish to validate a CSV file which does not have the f
names as the first line (i.e., the first line of the file is also data
+), then
use the C<-n> option to tell the program that the CSV files has "no he

B<WARNING>: You want to backup the database or CSV file before doing t
This program will copy the database or CSV file to the raw_data file a
+nd, if
all goes well, it will drop your tables (or CSV file) before proceedin
+g.  Then
it will attempt to re-add the data to the files.  If it does not succe
add the data, your data may very well be corrupted.

Also, the files or files created by validating B<will> have a header, 
C<DBD::CSV> automatically adds them, due to the way the module works. 
+ If this
is a problem, you should remove them yourself.

When you have completed validating a database, the raw data fill will 
+not be
unlinked.  I have left the file there if it's necessary to debug your

I strongly recommend using this feature if you have created an applica
+tion that
uses DBD::CSV.  Use your application, put it through its paces (with a
+ll the
tests you wrote, right?) and then use this application to test for dat


Copyright (c) 2001 Curtis "Ovid" Poe.  All rights reserved.
This program is free software; you may redistribute it and/or modify i
+t under
the same terms as Perl itself

=head1 AUTHOR

Curtis "Ovid" Poe <>
Address bug reports and comments to:

=head1 BUGS

2001/11/10 There are no known bugs at this time.  However, I modified 
+this pretty
heavily to get it "production ready".  Please let me know if there are
+ any issues
with it.

=head1 SEE ALSO

L<DBD::CSV>, L<DBI>, L<Text::CSV_XS> and L<SQL::Statement>.


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