Clean Up MySQL Code

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Hi All!

I have created a Perl script which connects to MySQL and fetchs data, the script is large and has many many instances of the section of code below:

    my $sql = "SELECT * from shop_items";
    my $sth   = $dbh->prepare($sql);
       $sth->execute;
    while (my $hash_ref = $sth->fetchrow_hashref)
      {
             # bla bla bla
      }
[download]

I'm trying to come up with a way of reducing that to just one line, maybe by using a subroutine but Im not sure how, my thinking is along the lines of:

   
   while(my $hash_ref = fetch_data("SELECT * FROM shop_items")) 
     {
           # bla bla bla
     }

  # SUBROUTINE FOR ALL CALLS

  sub fetch_data 
     {
           my $sql = @_;
           my $sth   = $dbh->prepare($sql);
              $sth->execute;
     }
[download]

I'm sure that's not quite right, but you get the drift of my thinking. Is this a good way to get rid of all those sections?

Thanks

Comment on Clean Up MySQL Code Select or Download Code

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Re: Clean Up MySQL Code by Juerd (Abbot) on Apr 20, 2003 at 15:36 UTC
`use DBIx::Simple; $db = DBIx::Simple->connect(...);` fetchrow_-ish: `my $result = $db->query('SELECT FROM shop_items'); while (my $row = $result->hash) { ... }` [download] Or, if it is okay to slurp all rows into memory, selectall_-ish: `for my $row ($db->query('SELECT FROM shop_items')->hashes) { ... }` [download] Note that slurping everything into memory is a bad idea in most cases. The same can be said about `SELECT *`. Juerd - http://juerd.nl/ - spamcollector_perlmonks@juerd.nl (do not use).	[reply] [d/l] [select]
Re: Clean Up MySQL Code by DrManhattan (Chaplain) on Apr 20, 2003 at 15:31 UTC
You can reduce three of your lines to one by using selectall_arrayref() like so: `my $results = $dbh->selectall_arrayref( "SELECT * FROM shop_items", { Slice => {} } ); foreach my $hash_ref (@$results) { # blah }` [download] If you want to write it as a subroutine, this would work: `sub fetch_data { my $dbh = shift; return $dbh->selectall_arrayref( "SELECT * FROM shop_items", { Slice => {} } ); }` [download] Then you could call it like this: `foreach my $hash_ref (@{&fetch_data($dbh)}) { # blah }` [download] -Matt	[reply] [d/l] [select]
Re: Clean Up MySQL Code by astaines (Curate) on Apr 21, 2003 at 09:42 UTC
Here's a slightly different approach - I create a load of SQL statements, put them in an array, `foreach my $sql (@sql) { unless ($sth=run_sql($sql)){ die "Failed in processing \"".$sql."\"\n"; } } #Use them like this... my $result = $sth->fetchall_arrayref;` [download] and then run them using this subroutine - `# #run_sql # subroutine that does all of the work # sub run_sql{ my $sql = shift; my $sth = $dbh->prepare($sql); if (!$sth) { die "Error:" . $dbh->errstr ." while preparing ".$sql."\n"; } if (!$sth->execute) { die "Error:" . $sth->errstr ." while executing ".$sql."\n"; } return $sth; } # run_sql` [download] The idea here is that I like to pass statement handles around ($sth), which I can then do whatever I want with. I find this much more flexible than passing result sets around. YMMV! Happpy Easter, -- Anthony Staines	[reply] [d/l] [select]