Beefy Boxes and Bandwidth Generously Provided by pair Networks
Clear questions and runnable code
get the best and fastest answer
 
PerlMonks  

Re: For loop suggestions

by roboticus (Chancellor)
on Jan 11, 2013 at 11:45 UTC ( #1012867=note: print w/ replies, xml ) Need Help??


in reply to For loop suggestions

sure_mp:

Ah, ignore me. I didn't read the original post closely enough, and answered the wrong question.

If you mean SQL database when you say database, then you can ask the database directly with something like:

... use DBI; ... my $DB = DBI->connect(...); my $ar = $DB->selectall_arrayref(<<EOSQL); SELECT min(colName) AS min_val, max(colName) AS max_val FROM tableName EOSQL print "Minimum value found: $$ar[0][0]\n" . "Maximum value found: $$ar[0][1]\n";

Typically, database engines keep statistics about table columns so they can optimize queries, so the database engine many not even have to scan through the table to find all the values.

On the other hand, if you're using a flat file, or a data structure in memory, your approach is almost good. But rather than scanning all possible values, you could just scan the records and track the minimum and maximum values:

my ($min, $max); for my $rec (@records) { $min = $$rec[$colNum] if !defined($min) or $$rec[$colNum]<$min; $max = $$rec[$colNum] if !defined($max) or $$rec[$colNum]>$max; } print "Values used are between $min and $max\n";

...roboticus

When your only tool is a hammer, all problems look like your thumb.


Comment on Re: For loop suggestions
Select or Download Code

Log In?
Username:
Password:

What's my password?
Create A New User
Node Status?
node history
Node Type: note [id://1012867]
help
Chatterbox?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others exploiting the Monastery: (6)
As of 2015-07-29 06:52 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    The top three priorities of my open tasks are (in descending order of likelihood to be worked on) ...









    Results (260 votes), past polls