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Re: For loop suggestions

by roboticus (Canon)
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.


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