I have a database with several tables in it, and each table contains data on
lots of people. From one run of my program to the next, the tables could
change, so my code needs to be fairly general.
I want to pull the data for each person from each table, and create an XML
report - one report for each person.
The problem I'm having is that my code is very inefficient. Although I've read
that putting prepare inside a loop is slow, I have failed to make anything else
work at all (I tried putting the connections into an array, but either I did
something wrong or that is not supposed to work).
I would be very grateful if someone were able to tell me how to rewrite this in
order to make if more efficient.
use DBI;
use IO::File;
use XML::Writer;
my $dbh = DBI->connect( 'DBI:SQLite:myDB' )
or die "Couldn't connect to database: ". DBI->errstr;
my $sth = $dbh->prepare( 'SELECT id FROM demography' )
or die "Couldn't prepare statement: " . $dbh->errstr;
my $id;
my @tables = $dbh->tables();
# Get the IDs
$sth->execute();
while( $id = $sth->fetchrow_array() ){
# Open report for writing and add top-matter here:
# code not shown
for (0..$#tables){
$theTable = $tables[$_];
$qid = $dbh->quote( $id );
# Do stuff to make the next line produce the correct SQL:
# code not shown
$sql = "SELECT * FROM $theTable WHERE usubjid = $id";
# Next lines are inefficient. Please help!
$cnx = $dbh->prepare($sql);
$cnx->execute()
or die "Failed execution";
# Code omitted here
} # Close while
# Tidy up and close down here
Many thanks,
Harry
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