I can think of a few ways of doing this -

Method 1 (row by row comparison, the code is not tested, just a general idea of how the code would look like)
#!/usr/bin/perl -w
use strict;
use DBI;
use DBD::Oracle;

my $db1 = DBI->connect("dbi:Oracle:server=XXXX;database=XXXX", "USER",
+"PASSWD")
        or die "Failed to connect to the database!";

my $db2 = DBI->connect("dbi:Oracle:server=XXXX;database=XXXX", "USER",
+"PASSWD")
        or die "Failed to connect to the database!";
        
my $table = "DUMMY";        # name of the table
my $unique_id = "ID";       # unique id to identify the row

my $sth1 = $db1->prepare( "select * from $table" );
my $sth2 = $db2->prepare( "select * from $table where $unique_id=?" );

$sth1->execute();
while (my $row = $sth1->fetchrow_hashref())
{
    my $found = 0;

    $sth2->execute( $row->{$unique_id} );
    while (my $row2 = $sth2->fetchrow_hashref()) {
        # compare the row
        foreach (keys %$row) {
            if ($row{$_} ne $row2{$_}) {
               print "DIFF: (ID) $_\n";
               break;
            }
        }
    }
}

$sth->finish;
$dbh->disconnect;

[download]

Method 2 - DBA way

step 1 - copy both tables into a dummy database, name the tables dummy1 and dummy2

step 2 - copy dummy1 to new table dummy3

step 3 - SQL: delete from dummy1 where ID is found in dummy2

step 4 - delete from dummy3 where ID is found in dummy1

step 5 - delete from dummy2 where ID is found in dummy 3

So in the end, dummy3 holds records in both the original dummy1 and dummy2 tables, and dummy1, dummy2 hold records that do not reconcile.

Method 3 - pg way

Have to say that pg's method is much clever.

In reply to Re: need to look for data differences in same table in two database instances by Roger
in thread need to look for data differences in same table in two database instances by Anonymous Monk

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