DBI: How to find the right data-types for unknown data? - database

Question

With of these two approaches would you prefer: trying to find the right data-types or simply using always varchar?
# ...
use HTML::TableExtract;
my $te = HTML::TableExtract->new( headers => [ 'some headers', 'one', 'two' ], keep_headers => 1 );
$te->parse( $html_string );
die $te->tables if $te->tables != 1;
( my $grid ) = $te->tables;
use DBI;
my $dbh = DBI->connect( ... ) or die $DBI::errstr;
my $table = 'my_test_table';
my #rows = $grid->rows;
my $header_row = shift #rows;
##### version 1 ####
use Data::Types qw(:all);
my #create_row;
for my $col ( 0 .. $#$header_row ) {
my ( $count, $int, $float ) = ( 0, 0, 0 );
my $longest = 0;
for my $row ( #rows ) {
$longest = length $row->[$col] if length $row->[$col] > $longest;
$int++ if is_int( $row->[$col] );
$float++ if is_float( $row->[$col] );
$count++;
}
if ( $int == $count ) {
$create_row[$col] = $dbh->quote( $header_row->[$col] ) . ' int';
}
elsif ( $float == $count ) {
$create_row[$col] = $dbh->quote( $header_row->[$col] ) . ' float';
}
else {
$create_row[$col] = $dbh->quote( $header_row->[$col] ) . " char($longest)";
}
}
$sql = sprintf "CREATE TABLE $table ( %s )",
join( ', ', #create_row );
$dbh->do( $sql );
$sql = sprintf "INSERT INTO $table ( %s ) VALUES( %s )",
join( ',', map { $dbh->quote( $_ ) } #$header_row ), join( ',', ('?') x #$header_row );
my $sth = $dbh->prepare( $sql );
#### version 2 ####
# always varchar
$sql = sprintf "CREATE TABLE $table ( %s )",
join( ', ', map { "'$_' varchar(60)" } #$header_row );
$dbh->do( $sql );
$sql = sprintf "INSERT INTO $table ( %s ) VALUES( %s )",
join( ',', map { $dbh->quote( $_ ) } #$header_row ), join( ',', ('?') x #$header_row );
my $sth = $dbh->prepare( $sql );

Answer 1

If the table you're processing will not change, and if the column will only be used for that single table's data, then it is safe to guess a data type that seems to fit (version 1).
However, if you plan to add any more data to that column then you'd need to keep everything as varchars in case there's some data of a different type in future (version 2).