If you only need the first three characters of each column, why not simply ask for that when doing your query? For example:

SELECT SUBSTR(COL1, 0, 3) FROM TABLENAME;
[download]

Consider using place holders where possible, See DBI and Bobby Tables.

That will work.. But, I actually wanted to extract 6 characters for the 3 column... How do I achieve that??

Replace the 3 in my example with a 6, you should consider learning basic SQL.

Nitpick: even though substr() is implemented in most sql dialects, the standards-compliant function is substring(col1 from 1 for 3)

OP stated they're using Oracle, substring(col1 from 1 for 3) doesn't work (ORA-00907). substr.

I'm not sure you pasted actual code, as that would warn a lot. Why did you comment 'use strict;'? And why is 'use warnings;' missing? I am absolutely sure it will give you all the hints you need …

my $dbh = DBI->connect($server,$user,$passwd,$dbd, {RaiseError => 1,Au
+toCommit => 1 });
                                             ^? read the docs again
# Prepare the SQL query for execution
my $sql = "SELECT $ans_rid, $ans_qcn, $ans_loc FROM ft_int_tbl WHERE $
+ans_rid is not null";
                  ^?        ^?        ^?                             ^
+?
my $sth = $dbh->prepare($sql) or die "Couldn't prepare statement:$DBI:
+:errstr; stopped";
                              ^? you set RaiseError, so you'll never g
+et that
# Execute the query
$sth->execute() or die "Couldn't execute statement: $DBI::errstr; stop
+ped";
                ^? same here
#open JKLL, ">$an_dt_file" or die "can't open file $ansb_detail_file f
+or write,\n";

# Fetch each row and print it
while ( my ($ans_rid, $ans_qcn, $ans_loc) = $sth->fetchrow_array() ) {
my ($ansb_cktid, $ansb_mcn, $ansb_soc) = unpack("A3 A3 A3", $_);
                                                            ^? what do
+ you expect to be in $_
#print JKLL"Field 1: $ansb_cktid Field 2:$ansb_mcn Field 3: $ansb_soc 
+\n";
print "Field 1: $ansb_cktid Field 2:$ansb_mcn Field 3: $ansb_soc \n";
}

==> corrected based on guesses, as I have no idea

my $dbh = DBI->connect ($server, $user, $passwd, {
    RaiseError         => 1,
    PrintError         => 1,  # Comes in very handy when you are runni
+ng into trouble
    ShowErrorStatement => 1,  # this too
    AutoCommit         => 1,
    });
# Prepare the SQL query for execution
my $sql = "SELECT ans_rid, ans_qcn, ans_loc FROM ft_int_tbl WHERE ans_
+rid is not null";
my $sth = $dbh->prepare ($sql);

# Execute the query
$sth->execute ();
#open JKLL, ">$an_dt_file" or die "can't open file $ansb_detail_file f
+or write,\n";

# Fetch each row and print it
while (my ($ans_rid, $ans_qcn, $ans_loc) = $sth->fetchrow_array ()) {
    my ($ansb_cktid, $ansb_mcn, $ansb_soc) = unpack "A3 A3 A3", $ans_l
+oc;
    print "Field 1: $ansb_cktid Field 2:$ansb_mcn Field 3: $ansb_soc \
+n";
    }
[download]

Tux,

while (my ($ans_rid, $ans_qcn, $ans_loc) = $sth->fetchrow_array ()) {
    my ($ansb_cktid, $ansb_mcn, $ansb_soc) = unpack "A3 A3 A3", $ans_l
+oc;
[download]

This unpacks only the 3rd column ie, $ans_loc... I wanted to unpack all the 3 columns..ie, $ans_rid, $ans_qcn, $ans_loc and have the values stored in $ansb_cktid, $ansb_mcn, $ansb_soc..

Then you need to unpack all 3, you can't unpack three variables at once AFAIK. The "A3 A3 A6" is a format for unpacking one variable, as Tux showed in the example. You could just used substrings,

$ans_rid = substr($ans_rid, 0, 3);
$ans_qcn = substr($ans_qcn, 0, 3);
$ans_loc = substr($ans_loc, 0, 6);
[download]

..or make new variables for each substr() leaving the original variable intact.