My Perl script is supposed to print the results from my query. However, at the moment I'm getting the error:
Can't locate object method "fetchrow_array" via package "SELECT * FROM SERVER" (perhaps you forgot to load "SELECT * FROM SERVER"?) at updateDB.pl line 32
I imagine the problem is an easy one to fix.. but my perl / MySQL skills have much to be desired. My script is below:
#!/usr/bin/perl
use DBI;
use DBD::mysql;
use strict;
use warnings;
MySQL("SELECT * FROM SERVER");
# define subroutine to submit MySQL command
sub MySQL
{
# establish connection with 'serverDNA' database
my $connection = DBI->connect("DBI:mysql:database=serverDNA;host=localhost");
my $query = $_[0]; #assign argument to string
my $statement = $connection->prepare($query); #prepare query
$statement->execute(); #execute query
#loop to print MySQL results
while (my #row = $query->fetchrow_array)
{
print "#row\n";
}
}
Thanks so much!
You're calling fetchrow_array on the query string; you want to call it on the statement.
while (my #row = $statement->fetchrow_array)
{
print "#row\n";
}
Related
I can't seem to figure out the issue with my .pm file and script. I am fairly new to Perl.
I have a database with name "project" and there is table with name "mailing".
mailing table has 7 entries, which I want to display using module.
So, I have this custom module to log in to database and do a query. This module is names as DB.pm
DB.pm is stored on my FEDORA 20 at /root/mysql/GUI/DB.pm.
DB.pm is defined as follows:
package GUI::DB;
use strict;
use DBI;
use vars qw(#ISA #EXPORT);
use Exporter;
#ISA = qw(Exporter);
#EXPORT = qw(dbConnect query);
#
# dbConnect - connect to the database, get the database handle
#
sub dbConnect {
# Read database settings from config file:
print "Works";
my $dsn = "DBI:mysql:project";
my $dbh = DBI->connect( $dsn,
'root',
'mydatabasepassword',
{ RaiseError => 1 }
);
return $dbh;
}
#
# query - execute a query with parameters
# query($dbh, $sql, #bindValues)
#
sub query {
my $dbh = shift;
my $sql ="SELECT * FROM mailing";
my #bindValues = #_; # 0 or serveral parameters
my #returnData = ();
# issue query
my $sth = $dbh->prepare($sql); //**line number 39 that is giving** error
if ( #bindValues ) {
$sth->execute(#bindValues);
} else {
$sth->execute();
}
if ( $sql =~ m/^select/i ) {
while ( my $row = $sth->fetchrow_hashref ) {
push #returnData, $row;
}
}
# finish the sql statement
$sth->finish();
return #returnData;
}
1;
Now I want to use this module inside my per script. This is what I tried:
#!/usr/bin/perl
use warnings;
use strict;
use lib '/root/mysql/';
use GUI::DB qw(dbConnect query);
dbConnect();
query();
This is the error I'm getting -->
Can't call method "prepare" on an undefined value at /root/mysql/GUI/DB.pm line 39.
Please help me with this. I am not sure how to proceed. I am guessing it has something to do with argument passing. Nothing is wrong with database. It works fine from CLI.
Thanks :)
_x_X_X_X_X_X_X_X_X_X_X_X_X_X_X_X__X_X_X_X_X__X
TILL HERE IT IS RESOLVED
_X_X_X_X_X_X_X_X_X_X_X_X_X_X_X_X_X__X_X_X
FURTHER ISSUE is SQL command is not working.
In the mailing table of my database I have email id with different domains.
For example, some id's are xyz#gmail.com, 12343#gmail.com , bae#yahoo.com as so on and I am assuming new email ids will be added to mailing tables every day with different domains.
I am trying to write a scripts that updates another table which holds a daily count of email addresses by their domain name. This is what I tried:
#!/usr/bin/perl
use warnings;
use strict;
use lib '/root/mysql/';
use 5.016;
use Data::Dumper;
use GUI::DB qw(dbConnect query);
my $data = dbConnect();
my #domain = query($data, "SELECT substr(addr,locate('\#',addr)+1) as maildomain, count (*) as mailcount FROM mailing GROUP BY maildomain ORDER BY mailcount DESC");
for my $key (#domain){
say Dumper ($key);
}
But I am getting an error,
You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '*) as mailcount FROM mailing GROUP BY maildomain ORDER BY mailcount DESC' at line 1 at /root/mysql/GUI/DB.pm line 44.
Same SQL statement works from CLI with no issues.
Any help would be appreciated. :)
1) Your error is saying that $dbh is undefined here:
sub query {
my $dbh = shift;
...
# issue query
my $sth = $dbh->prepare($sql); #<***LOOK HERE***
...which means $dbh must be undefined here:
sub query {
my $dbh = shift; #<***LOOK HERE***
...
# issue query
my $sth = $dbh->prepare($sql);
2) Let's see why. Your dbConnect() method returns $dbh:
sub dbConnect {
# Read database settings from config file:
print "Works";
my $dsn = "DBI:mysql:project";
my $dbh = DBI->connect(
$dsn,
'root',
'mydatabasepassword',
{ RaiseError => 1 }
);
return $dbh; #<***LOOK HERE*****
}
3) But, you call dbConnect() like this:
dbConnect();
Because you never save the return value anywhere, $dbh is discarded.
4) Furthermore, you call query() like this:
query();
Yet, you defined query() like this:
sub query {
my $dbh = shift;
The query() sub believes that the first argument will be the database handle--but you didn't call query() with any arguments.
You need to do this:
my $data_base_handle = dbConnect();
my #results = query($data_base_handle);
#do something with #results
Response to comment:
I printed #results, this is what I see HASH(0x1d05be8)
HASH(0x1d05ba0) HASH(0x1d05b58) HASH(0x1d05b10) HASH(0x1d05ac8)
HASH(0x1d05a80) HASH(0x1d05a38)
You wrote:
my $row = $sth->fetchrow_hashref;
...which asks DBI to return each row as a reference to a hash. Then you wrote:
push #returnData, $row;
...which pushed each hash reference into an array. So query() returns an array of hash references. The notation HASH(0x1d05be8) is what perl outputs when you print a hash reference.
If you want to see what's in those hashes, then do this:
use 5.016; #enable say()
use Data::Dumper;
...
...
for my $href (#results) {
say Dumper($href);
}
To access the data in a hash reference, you can do this:
use strict;
use warnings;
use 5.016;
use Data::Dumper;
my $href = {
c => 3,
a => 1,
b => 2,
};
my %hash = %{$href}; #dereference, {}, the reference into a hash, %
for my $key ( keys %hash ) {
say "$key $hash{$key}";
}
--output:--
c 3
a 1
b 2
Response to next comment:
(Answer posted in comments under op.)
By the way, perl is pretty good at text processing, so if you couldn't figure out the problem with your query, you could process the email addresses with perl:
use strict;
use warnings;
use 5.012;
use Data::Dumper;
use DBI;
use DBD::mysql;
# CONFIG VARIABLES
my $db_type = "mysql";
my $database = "my_db";
my $host = "localhost";
my $port = "3306";
my $user = "root";
my $pword = "";
# DATA SOURCE NAME
my $dsn = "dbi:$db_type:$database:$host:$port";
# PERL DBI CONNECT
my $dbh = DBI->connect($dsn, $user, $pword);
# PREPARE THE QUERY
my $tablename = "mailing";
my $select =<<"END_OF_SELECT";
select addr from $tablename
END_OF_SELECT
my $addr_aref = $dbh->selectcol_arrayref($select); #Returns a reference to a flat array containing all the email addresses
$dbh->disconnect;
my %count_for;
for my $addr (#{$addr_aref}) {
$addr =~ s/.*#//;
$count_for{$addr}++;
}
say Dumper(\%count_for);
--output:--
$VAR1 = {
'google.com' => 2,
'gorilla.com' => 1,
'yahoo.com' => 3
};
I've researched a bit and found that using mysql_use_result=1 is supposed to alleviate the memory issue. However, since I am new to this DBI module I don't understand what is happening here:
#!/usr/bin/perl -w
use strict;
use DBI;
my $dbh = DBI>connect('DBI:mysql:blah;host=blah.blah.blah.blah;mysql_use_result=1','blah','blah',{RaiseError => 1});
my $sth = $dbh->prepare('select * from TaqMinute where tradeDate<=\'2014-04-22\' and symbol<=\'AAPL\' ;') ;
if (defined($sth)) {
$sth->execute();
my #row;
while (#row = $sth-> fetchrow_array()) {
print "#row\n" ;
}
}
$sth->finish();
$dbh->disconnect
Before I added mysql_use_result=1, the script would fail after about 1.5 minutes complaining that it ran out of memory. After adding this my query arguments are ignored and I simply get all the data in the database.
Any ideas how to help me or how to use this switch properly? Btw, the database that I am querying is very large.
Thanks in advance!
Craig
Try to use parametized queries, maybe something wrong with your qoutes.
my $dbh = DBI>connect('DBI:mysql:blah;host=blah.blah.blah.blah','blah','blah',{RaiseError => 1});
my $sth = $dbh->prepare_cached('select * from TaqMinute where tradeDate<=? and symbol<=?') ;
die "sth undef!" if ! defined $sth;
$sth->execute('2014-04-22','AAPL');
while (my $rowref = $sth->fetchrow_arrayref()) {
print Dumper($rowref) ;
}
$sth->finish;
I've created a Perl script which is meant to loop through an array (a shortlist of customers who meet certain criteria), execute an external command using system() , then update a field within each row once the operation has completed.
It works on the first record (ie external command executes, customer record updates), however when it gets to the second record I receive this error:
DBD::mysql::st fetchrow_array failed: fetch() without execute() at customer_update.pl
Through some googling I added the $sth->finish(); command, however whether I include it or not (either inside the loop as shown, or straight afterward) I still get the same error.
Can anyone shed any light for me as to what I am doing wrong here?
Here's an extract:
# PERL MYSQL CONNECT()
$dbh = DBI->connect('dbi:mysql:signups', $user, $pw)
or die "Connection Error: $DBI::errstr\n";
# DEFINE A MySQL QUERY
$myquery = "SELECT * FROM accounts WHERE field3 = false";
$sth = $dbh->prepare($myquery);
# EXECUTE THE QUERY
$sth->execute
or die "SQL Error: $DBI::errstr\n";
#records = $sth->rows;
print "Amount of new customers: #records\n\n";
while ( my ($field1, $field2, $field3) = $sth->fetchrow_array() ) {
#execute external command via system();
$update_customer_status = "UPDATE accounts SET field3=true WHERE id=$id";
$sth = $dbh->prepare($update_customer_status);
$sth->execute
or die "SQL Error: $DBI::errstr\n";
print "Customer record modified & MySQL updated accordingly\n\n";
$sth->finish();
}
Building a SQL statement with variables and then prepare()ing it defeats the purpose of the prepare. You should build the SQL statement with a placeholder ? instead of $id, prepare() it, and then execute($id) it. As it is, you are leaving yourself open to SQL injection attacks.
Also, it seems that you are not using the warnings and strict pragmas. These two lines should be at the top of every program you write:
use warnings;
use strict;
They will save you much heartache and frustration in the future.
In your loop, you overwrite the handle over from which you are fetching. Use a different variable. (Changing $sth = ...; to my $sth = ...; will do.) While we're at it, let's move the prepare out of the loop.
my $sth_get = $dbh->prepare("SELECT * FROM accounts WHERE field3 = false");
my $sth_upd = $dbh->prepare("UPDATE accounts SET field3=true WHERE id = ?");
$sth_get->execute();
while ( my ($field1, $field2, $field3) = $sth_get->fetchrow_array() ) {
...
$sth_upd->execute($id);
}
You are stomping on your $sth variable when you execute this line ...
$sth = $dbh->prepare($update_customer_status);
Why not save off the result of $sth->fetchrow_array() to an array variable.
Something like ...
my #select_results_AoA = $sth->fetchrow_array();
... and then iterate over the array ...
for my #row ( #select_resilts_AoA ) {
... instead of ...
while ( my ($field1, $field2, $field3) = $sth->fetchrow_array() ) {
I have written the following code in Perl. I have ActivePerl 5.14 for Windows 7.
#!C:\perl64\bin\perl.exe -wT
use strict;
use warnings;
use DBI;
print "Content-type: text/html \n\n";
# MYSQL CONFIG VARIABLES
my $driver = "mysql";
my $database = "test555";
my $tablename3 = "test77";
my $user = "root";
my $pw = "root";
# PERL MYSQL CONNECT()
my $dbh = DBI->connect("DBI:$driver:$database", $user, $pw,);
my $sth = $dbh->prepare("
SELECT *
FROM t6
WHERE paragraph='PWE1234'
");
$sth->execute();
#$dbh->disconnect;
#exit 0;
When the program reaches $dbh->disconnect, the system is throwing an error; hence commented it out. When I comment that out, the system is not throwing any error, but neither do I get output.
There is a result for this query, I checked with MySQL once separately.
There is no output because you have no code to create any output.
After calling execute you need to call one of the fetchsomething methods and do something with the data structure you get back.
I am doing the following, and getting "1" which I assume means the statement wend well. But I would like the result instead.
What's wrong?
#!/usr/bin/perl
use strict;
use DBI;
my $host = "test";
my $database = "dd";
my $port = 3306;
my $user = "uuu";
my $pw = "ppp";
my $mysql = DBI->connect("DBI:mysql:database=$database;host=$host;port=$port", $user, $pw)
or die "Cannot connect to MySQL server\n";
my $m = $mysql->do(qq{select MAX(idvisit) from log_visit});
print $m;
my $m = $mysql->prepare("select MAX(idvisit) from log_visit");
$m->execute() or die "Couldn't execute statement: ".$m->errstr;
print $m->fetch()->[0];
It's always worth checking the documentation for functions that you're having trouble with.
In this case the DBI documentation for "do" says:
Prepare and execute a single
statement. Returns the number of rows
affected or undef on error.
And, more explicitly,
It should not be used for SELECT
statements because it does not return
a statement handle (so you can't fetch
any data).
do returns the number of affected rows. You might want to look into the statement class and specifically, the execute function.
my $m = $mysql->selectrow_array(qq{select MAX(idvisit) from log_visit});