Working with some existing code to pull data from a MySQL database I ran the following code:
\n
\n$SQL = "SELECT id FROM `sensors` ";\n$SQL .= "WHERE `storage_table` LIKE '$source_temperature_table' ";\n\n$r = $db->query($SQL);\nmy $src_sensor_id = $r->getNextRow();\nprint "The id is $src_sensor_id \\n";<\/code><\/pre><\/p>\nNo matter which table I ran this on, I always got 1 as the id. So I tried looking at the value of $r using print $r; and the correct ID was showing up. The reason is that perl is different from other languages that I use when it comes to arrays. When I thought I assigned the only value in $r to $src_sensor_id, what I was really doing was assigning the count of the number of rows in $r to $src_sensor_id. When I printed $r, the print statement printed all of the values in the array $r because that\u2019s how print statements handle arrays.<\/p>\n
The correct way to assign the array values in $r to variables is to put parentheses around the list of variables in the array. e.g.
\n
\nmy ($src_sensor_id) = $r->getNextRow();<\/code><\/pre><\/p>\nIf you have multiple items in the array, separate the variables with commas. e.g.
\n
\nmy ($src_sensor_id, $location, $name) = $r->getNextRow();<\/code><\/pre><\/p>\n","protected":false},"excerpt":{"rendered":"Working with some existing code to pull data from a MySQL database I ran the following code: $SQL = "SELECT id FROM `sensors` "; $SQL .= "WHERE `storage_table` LIKE '$source_temperature_table' "; $r = $db->query($SQL); my $src_sensor_id = $r->getNextRow(); print "The id is $src_sensor_id \\n"; No matter which table I ran this on, I always got 1 … Continue reading Perl gotcha\u2019s\u2013arrays<\/span><\/a><\/p>\n","protected":false},"author":6,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[32],"tags":[],"class_list":["post-2344","post","type-post","status-publish","format-standard","hentry","category-perl"],"_links":{"self":[{"href":"https:\/\/www.wellgolly.com\/index.php?rest_route=\/wp\/v2\/posts\/2344","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.wellgolly.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.wellgolly.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.wellgolly.com\/index.php?rest_route=\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/www.wellgolly.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=2344"}],"version-history":[{"count":0,"href":"https:\/\/www.wellgolly.com\/index.php?rest_route=\/wp\/v2\/posts\/2344\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.wellgolly.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=2344"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.wellgolly.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=2344"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.wellgolly.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=2344"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}