<?php
include('connnect.php');
db_connect();
echo 'We're about to count some rows';
$query = "SELECT COUNT(*) FROM accounts";
$result = mysqli_query($mysqli,$query);
$row = $result->fetch_row();
echo $row[0];
?>
I can't seem to find out how to get the number of rows(users) in the accounts table, this code simply returns nothing. I'm not sure if I'm passing the right information into 'num_rows' or if the query that I'm using is correct.
I went ahead and ran a test where one query uses a prepared statement, and the other builds the entire query then executes that. I'm probably not making what I'm wanting to know easy to understand.
Here's my test code. I was thinking prepared statements sort of held back execution until a $stmt->close() was called to optimize it or something. That doesn't appear to be the case though as the test that builds the query using real_escape_string is at least 10 times faster.
<?php
$db = new mysqli('localhost', 'user', 'pass', 'test');
$start = microtime(true);
$a = 'a';
$b = 'b';
$sql = $db->prepare('INSERT INTO multi (a,b) VALUES(?, ?)');
$sql->bind_param('ss', $a, $b);
for($i = 0; $i < 10000; $i++)
{
$a = chr($i % 1);
$b = chr($i % 2);
$sql->execute();
}
$sql->close();
echo microtime(true) - $start;
$db->close();
?>
This actually depends on the Mysql server. The default max size for all data combined in the entire query is 1mb. See: http://dev.mysql.com/doc/refman/5.1/en/packet-too-large.html
If your data combined is under that "max_allowed_packet" threshold, just use "s" for the binding type for any text field. Infact, you can usually get away with using "s" for any field type at all (date, float, etc).
If your entire entry combined that you want to insert is over 1mb (or whatever you reset it to) in length, you'll want to use mysqli_stmt::send_long_data method and the "b" binding type to send this particular field in chunks.
You can efficiently get a count of all entities of a particular kind (i.e., number of rows in a table) using the Datastore Statistics. Simple example:
from google.appengine.ext.db import stats
kind_stats = stats.KindStat().all().filter("kind_name =", "NameOfYourModel").get()
count = kind_stats.count
You can find a more detailed example of how to get the latest stats here (GAE may keep multiple copies of the stats - one for 5min ago, one for 30min ago, etc.).
Note that these statistics aren't constantly updated so they lag a little behind the actual counts. If you really need the actual count, then you could track counts in your own custom stats table and update it every time you create/delete an entity (though this will be quite a bit more expensive to do).
Update 03-08-2015: Using the Datastore Statistics can lead to stale results. If that's not an option, another two methods are keeping a counter or sharding counters. (You can read more about those here). Only look at these 2 if you need real-time results.
Select tr elements from tbody and use slice method to select a range of them:
$("table > tbody > tr").hide().slice(0, 2).show();
Demo:
$("table > tbody > tr").hide().slice(0, 2).show();
$(".show-all").on("click", function() {
$("tbody > tr", $(this).prev()).show();
});<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<table>
<tbody>
<tr>
<td>1</td>
<td>Alice</td>
</tr>
<tr>
<td>2</td>
<td>Bob</td>
</tr>
<tr>
<td>3</td>
<td>Carol</td>
</tr>
</tbody>
</table>
<button class="show-all">Show all</button>
.slice( start [, end ] )Reduce the set of matched elements to a subset specified by a range of indices.
startType: Integer
An integer indicating the 0-based position at which the elements begin to be selected. If negative, it indicates an offset from the end of the set.
endType: Integer
An integer indicating the 0-based position at which the elements stop being selected. If negative, it indicates an offset from the end of the set. If omitted, the range continues until the end of the set.
or