StackOverflow2013

Note that there are some explanatory texts on larger screens.

plurals

PO
primarykey
Id
17896210
data
AcceptedAnswerId
0
AnswerCount
0
ClosedDate
CommentCount
0
CommunityOwnedDate
CreationDate
2013-07-27T09:17:38.943
FavoriteCount
0
LastActivityDate
2013-07-27T09:17:38.943
LastEditDate
LastEditorUserId
0
OwnerUserId
1521179
ParentId
17895308
PostTypeId
2
Score
6
ViewCount
0
LastEditorDisplayName
text
Body
The Problem is that you aren't properly declaring your variables. For every script, you should <pre class="lang-perl prettyprint-override"><code>use strict; use warnings; </code></pre> This disallows common error sources, warns about iffy stuff, and forces you to properly declare all your variables. By default, all undeclared variables are considered global. Therefore, in <pre><code>for($i=0;$i<=9;$i++) { @Space = (); push(@Hits,\@Space); } </code></pre> the <code>@Space</code> refers to the same array in each iteration. Ergo, all ten entries in <code>@Hits</code> are a reference to the same array. Let's inspect what <code>@Hits</code> actually is. We can do so with <code>Data::Dumper</code> or the <code>Data::Dump</code> module (the latter usually produces prettier output): <pre><code>use Data::Dump; # use Data::Dumper; dd \@Hits; # print Dumper \@Hits; </code></pre> We get with <code>Data::Dumper</code> (easier to understand): <pre><code>$VAR1 = [ [ 1, 3, 5, 7 ], $VAR1->[0], $VAR1->[0], $VAR1->[0], $VAR1->[0], $VAR1->[0], $VAR1->[0], $VAR1->[0], $VAR1->[0], $VAR1->[0] ]; </code></pre> <hr> So I said the solution would be declaring your variables. Specifically, we want lexical variables. These variables are only visible inside the block where they are declared. This makes reasoning about code much easier. We can declare a lexical variable like so: <pre><code>my $foo = 123; </code></pre> When we have a loop like <pre><code>my @Hits; for my $i (0 .. 9) { my @Space; push @Hits, \@Space; } </code></pre> then each time the <code>my</code> is executed, we get a new <code>@Space</code>. Oh, and I have used a foreach-loop, that iterates over the range <code>0 .. 9</code> with the (lexical) <code>$i</code> variable. I find this easier to understand than the C-style loops you used. Because every element in <code>@Hits</code> now is a different arrayref, we get the expected data structure. As <code>Data::Dump</code> output: <pre><code>[[], [1], [], [3], [], [5], [], [7], [], []] </code></pre> When we now execute your loop that prints out the first value of each sub-array, then you may be suprised by the empty lines in between the numebers. This is because e.g. the first arrayref does not have an entry at index <code>0</code>, and therefore returns the special <code>undef</code> value. When used as a string, this is the empty string. If you followed my advice and did the <code>use warnings</code>, you also get a message that you are printing an uninitialized value. We can solve this by testing for definedness, and providing a zero otherwise. Since perl5 v10, we can use the defined-or operator <code>//</code> for this (on earlier perls, the <code>||</code> logical or has to do). <pre><code>for my $i (0 .. 9) { my $value = $Hits[$i][0] // 0; print "$value\n"; } </code></pre> There are a few other bits we can improve: <ul> <li>We don't have to manually create the <code>@Space</code> arrays; Perl does this behind the scenes when you dereference an array entry like <code>@{ $Hits[$i] }</code>. This is called autovivification.</li> <li>Not only can we iterate over ranges, but also over arrays. This is much better than hardcoding indices.</li> <li>Since v10, you can use the <code>say</code> feature. The <code>say</code> function is exactly like <code>print</code> but appends a newline at the end.</li> </ul> Here is how I'd have written that code: <pre><code>#!/usr/bin/perl use strict; use warnings; use feature 'say'; my @Hits; for my $i (1, 3, 5, 7) { push @{ $Hits[$i] }, $i; } for my $arrayref (@Hits) { say $arrayref->[0] // 0; } </code></pre> Output: <pre><code>0 1 0 3 0 5 0 7 </code></pre> (Note that we never initialized values at positions 8 and 9, so they are not shown. We could amend this by iterating over the slice <code>@Hits[0 .. 9]</code>.)
Tags
Title
singulars
PostAcceptedAnswerId
1. This table or related slice is empty.
PostParentId
1. POHow to push data to a multidimensional array?
 singulars
 PostTypePostTypeId
 PTQuestion
PostTypePostTypeId
1. PTAnswer
UserLastEditorUserId
1. This table or related slice is empty.
UserOwnerUserId
1. USamon
plurals
PostLinksPostIdRelatedPostId
1. This table or related slice is empty.
PostLinksRelatedPostIdPostId
1. This table or related slice is empty.
PostsAcceptedAnswerId
1. POHow to push data to a multidimensional array?
 singulars
 PostTypePostTypeId
 PTQuestion
PostsParentIdCreationDate
1. This table or related slice is empty.
VotesPostIdCreationDate
1. VO
 singulars
 PostPostId
 PO
 UserUserId
 This table or related slice is empty.
 VoteTypeVoteTypeId
 VTUpMod
2. VO
 singulars
 PostPostId
 PO
 UserUserId
 This table or related slice is empty.
 VoteTypeVoteTypeId
 VTAcceptedByOriginator
3. VO
 singulars
 PostPostId
 PO
 UserUserId
 This table or related slice is empty.
 VoteTypeVoteTypeId
 VTUpMod
CommentsPostId
1. This table or related slice is empty.

Querying!

Guidance

A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.