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POBoolean values in MySQL, Perl DBI, and JSON
 

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    <p>Consider a simple mysql table with columns <code>id</code> (an integer) and <code>flag</code> (a boolean). A user interface written in JavaScript communicates to a CGI backend via JSON, both for receiving data from the table and for updating it.</p> <p>Now, when sending the data <code>{id: 5, flag: true}</code> to the server, I of course use <code>from_json</code> to get a perl hash(ref). Then </p> <pre><code>my $sth = $dbh-&gt;prepare('UPDATE my_table SET flag = ? WHERE id = ?); $sth-&gt;execute($data-&gt;{flag}, $data-&gt;{id}); </code></pre> <p>always results in a false value being inserted. I believe this is because of the magic behaviour of JSON::true and JSON::false, which stringify to 'true' and 'false', respectively (but would numify to 1 and 0). Apparently, the execute statement provides string context, and not numeric context, so the mysql server receives a string containing no numbers, which then causes the value 0 to be inserted. For now, I fix this by putting <code>? 1 : 0</code> after <code>$data-&gt;{flag}</code>.</p> <p>In the other direction, the opposite wrong thing happens: According to DBI's doc, "Most data is returned to the Perl script as strings.", so when I hit the result of a SELECT query with <code>to_json</code>, the values are received by the UI as JavaScript strings "0" and "1", which are both true in JavaScript. So for now I do a <code>$_-&gt;{flag} += 0 foreach (@result)</code> before applying <code>to_json</code>.</p> <p>Question: At which point(s) in the chain should I insert these 'hacks'? In the JavaScript end, I could for example make sure to send the values 1 and 0 instead for true and false, and reread the flags as numbers. Is there something I can tell DBI to make it return numeric columns as (scalars which JSON would consider as) numbers? </p>
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