This is actually how your query works and is a normal behaviour. Using `LIMIT` you will not limit the count or sum but only the returned rows. So your query will return `n` rows as stated in your `LIMIT` clause. And since your query actually returns only one row, applying a (non-zero) limit has no effect on the results.

However, your second query will work as expected and is an established way of solving this problem.

I am trying to start httpd server on centos 6. It throws following error :

    [root@machine ~]# service httpd start
    Starting httpd: (13)Permission denied: make_sock: could not bind to address [::]:88
    (13)Permission denied: make_sock: could not bind to address 0.0.0.0:88
    no listening sockets available, shutting down
    Unable to open logs
                                                               [FAILED]

I have also checked for port 88, It is not is use.
I also checked with [semanage][1], but it didn&#39;t help.

Any help will be appreciated.


  [1]: http://rmohan.com/?p=1595

httpd Server not started: (13)Permission denied: make_sock: could not bind to address [::]:88

In the answer to &quot;https://stackoverflow.com/questions/9423170/how-is-amazon-dynamodb-throughput-calculated-and-limited&quot; it&#39;s been suggested, that DynamoDB throttles request whenever you exceed provisioned throughput on per second basis. However, this contradicts my experience.

I&#39;ve table where I post multiple rows, often the number of rows way exceeding provisioned write capacity. This happens in short bursts. At one point I&#39;ve even got 5 minutes average above provisioned capacity. OTOH, 15 minutes average is below capacity. I haven&#39;t got any throttled request in that period. 

5 minutes average peaks at 8.053 with provisioned capacity of 6:
![5 minutes average][1]

15 minutes average peaks well below provisioned capacity:

![enter image description here][2]

So when does DynamoDB throttle requests? What kind of average does it take in account? How high above provisioned capacity can the burst be before it gets throttled?


  [1]: http://i.stack.imgur.com/vYjGm.png
  [2]: http://i.stack.imgur.com/zbqvC.png

When does DynamoDB throttle request?

What I want to do is SUM a column, but also COUNT the number of rows it is summing, with a limit of no more than 5 rows. So my query is:

    SELECT COUNT(*), SUM(score) FROM answers WHERE user=1 LIMIT 5

What I expected back was a COUNT(*) up to 5 (I cant just assume it will always be 5 in my code logic as it could have less than 5 answers), with a sum of the score of the *up to* 5 rows.

Instead what I seem to get back is the total number of matching rows (where user is 1) as the count, and the sum of the score for those rows. The numbers don&#39;t change whether I put `LIMIT 1` or `LIMIT 5` or even `LIMIT 50`.

What I believe will work in this situation is this instead

    SELECT COUNT(*), SUM(score) FROM (SELECT * FROM answers WHERE user=1 LIMIT 5) AS a

But that seems a little convoluted for such a simple query, and as it&#39;s in a high traffic script, I want it to be as performant as possible.

Am I missing something? I did find [this bug report](http://bugs.mysql.com/bug.php?id=50005) from a few years back which seems to be related to this &quot;problem&quot;, but I&#39;m assuming it&#39;s not actually a bug?


MySQL COUNT with LIMIT

What I want to do is SUM a column, but also COUNT the number of rows it is summing, with a limit of no more than 5 rows. So my query is:
<pre><code class="hljs language-sql">SELECT COUNT(*), SUM(score) FROM answers WHERE user=1 LIMIT 5
</code></pre>
What I expected back was a COUNT(*) up to 5 (I cant just assume it will always be 5 in my code logic as it could have less than 5 answers), with a sum of the score of the up to 5 rows.
Instead what I seem to get back is the total number of matching rows (where user is 1) as the count, and the sum of the score for those rows. The numbers don't change whether I put <code>LIMIT 1</code> or <code>LIMIT 5</code> or even <code>LIMIT 50</code>.
What I believe will work in this situation is this instead
<pre><code class="hljs language-sql">SELECT COUNT(*), SUM(score) FROM (SELECT * FROM answers WHERE user=1 LIMIT 5) AS a
</code></pre>
But that seems a little convoluted for such a simple query, and as it's in a high traffic script, I want it to be as performant as possible.
Am I missing something? I did find <a href="http://bugs.mysql.com/bug.php?id=50005" target="_blank" rel="noopener noreferrer">this bug report</a> from a few years back which seems to be related to this "problem", but I'm assuming it's not actually a bug?

I have a table (&quot;lms_attendance&quot;) of users&#39; check-in and out times that looks like this:

    id	user	time	io (enum)
    1	9	1370931202	out
    2	9	1370931664	out
    3	6	1370932128	out
    4	12	1370932128	out
    5	12	1370933037	in

I&#39;m trying to create a view of this table that would output only the most recent record per user id, while giving me the &quot;in&quot; or &quot;out&quot; value, so something like:

    id	user	time	io
    2	9	1370931664	out
    3	6	1370932128	out
    5	12	1370933037	in

I&#39;m pretty close so far, but I realized that views won&#39;t accept subquerys, which is making it a lot harder. The closest query I got was :

    select 
        `lms_attendance`.`id` AS `id`,
        `lms_attendance`.`user` AS `user`,
        max(`lms_attendance`.`time`) AS `time`,
        `lms_attendance`.`io` AS `io` 
    from `lms_attendance` 
    group by 
        `lms_attendance`.`user`, 
        `lms_attendance`.`io`

But what I get is :

    id	user	time	io
    3	6	1370932128	out
    1	9	1370931664	out
    5	12	1370933037	in
    4	12	1370932128	out

Which is close, but not perfect. I know that last group by shouldn&#39;t be there, but without it, it returns the most recent time, but not with it&#39;s relative IO value.

Any ideas?
Thanks!

Select row with most recent date per user

I am using the following script to process a form to add info to my website. The problem I am having is when I submit the form nothing gets submitted to the database, and there are no errors. How can I add error reporting to my query?

    &lt;?php
    if (isset($_POST[&#39;itemdescription&#39;])) {$itemdescription = $_POST[&#39;itemdescription&#39;];}else {$itemdescription = &#39;&#39;;}
    if (isset($_POST[&#39;itemnumber&#39;])) {$itemnumber = $_POST[&#39;itemnumber&#39;];}else {$itemnumber = &#39;&#39;;}
    if (isset($_POST[&#39;sellerid&#39;])) {$sellerid = $_POST[&#39;sellerid&#39;];}else {$sellerid = &#39;&#39;;}
    if (isset($_POST[&#39;purchasedate&#39;])) {$purchasedatepre = $_POST[&#39;purchasedate&#39;];$date = DateTime::createFromFormat(&quot;D F d, Y&quot;, $purchasedatepre);$purchasedate = date(&#39;Y-m-d&#39;,strtotime($purchasedatepre));}else {$purchasedatepre = &#39;&#39;; $purchasedate = &#39;&#39;;}
    if (isset($_POST[&#39;otherinfo&#39;])) {$otherinfo = $_POST[&#39;otherinfo&#39;];}else {$otherinfo = &#39;&#39;;}
    if (isset($_POST[&#39;numberofitems&#39;])) {$numberofitems = $_POST[&#39;numberofitems&#39;];}else {$numberofitems = &#39;&#39;;}
    if (isset($_POST[&#39;numberofitemsused&#39;])) {$numberofitemsused = $_POST[&#39;numberofitemsused&#39;];}else {$numberofitemsused = &#39;&#39;;}
    if (isset($_POST[&#39;isitdelivered&#39;])) {$isitdelivered = $_POST[&#39;isitdelivered&#39;];}else {$isitdelivered = &#39;&#39;;}
    if (isset($_POST[&#39;price&#39;])) {$price = $_POST[&#39;price&#39;];}else {$price = &#39;&#39;;}
    
    $itemdescription = str_replace(&quot;&#39;&quot;, &quot;&quot;, &quot;$itemdescription&quot;);
    $itemnumber = str_replace(&quot;&#39;&quot;, &quot;&quot;, &quot;$itemnumber&quot;);
    $sellerid = str_replace(&quot;&#39;&quot;, &quot;&quot;, &quot;$sellerid&quot;);
    $otherinfo = str_replace(&quot;&#39;&quot;, &quot;&quot;, &quot;$otherinfo&quot;);
    
    include(&quot;connectmysqli.php&quot;); 
    
    mysqli_query($db,&quot;INSERT INTO stockdetails (`itemdescription`,`itemnumber`,`sellerid`,`purchasedate`,`otherinfo`,`numberofitems`,`isitdelivered`,`price`) VALUES (&#39;$itemdescription&#39;,&#39;$itemnumber&#39;,&#39;$sellerid&#39;,&#39;$purchasedate&#39;,&#39;$otherinfo&#39;,&#39;$numberofitems&#39;,&#39;$numberofitemsused&#39;,&#39;$isitdelivered&#39;,&#39;$price&#39;)&quot;);
    
    // header(&#39;Location: stockmanager.php?&amp;key=&#39;.$key);
    ?&gt;

How to display errors for my MySQLi query?

Let&#39;s say I am doing a MySQL `INSERT` into one of my tables and the table has the column `item_id` which is set to `autoincrement` and `primary key`.

**How do I get the query to output the value of the newly generated primary key `item_id` in the same query?**

Currently I am running a second query to retrieve the id but this hardly seems like good practice considering this might produce the wrong result...

If this is not possible then what is the best practice to ensure I retrieve the correct id?

Get the new record primary key ID from MySQL insert query?

I have this query in SQL, and I want it to implement it in LINQ using [Entity Framework][1], but how can I apply multiple tables left outer joins?

    SELECT d.bookingid,
           d.labid,
           d.processid,
           p.prid,
           p.prno,
           d.DestinationBranchID,
           d.SendStatus
    FROM   dc_tpatient_bookingd d
           LEFT OUTER JOIN dc_tpatient_bookingm m ON d.bookingid = m.bookingid
           LEFT OUTER JOIN dc_tpatient p ON p.prid = m.prid
           LEFT OUTER JOIN dc_tp_test t ON d.testid = t.testid
           LEFT OUTER JOIN dc_tp_groupm gm ON t.groupid = gm.groupid
           LEFT OUTER JOIN dc_tpanel pn ON m.panelid = pn.panelid
           LEFT OUTER JOIN dc_tp_organization og ON og.orgid = m.clientid
           LEFT OUTER JOIN dc_tp_ward w ON w.wardid = m.wardid
           LEFT OUTER JOIN dc_tp_branch tb ON tb.BranchID = m.BranchID
    WHERE  d.processid = 6
           AND ( ( m.branchId = 1
                   AND d.DestinationBranchID = 0 )
                  OR ( d.DestinationBranchID = 1
                       AND d.sendstatus = &#39;R&#39; ) )
           AND d.testid IN (SELECT testid
                            FROM   dc_tp_test
                            WHERE  subdepartmentid = 13)
           AND date_format(m.enteredon, &#39;%Y/%m/%d&#39;) BETWEEN &#39;2013/06/15&#39; AND &#39;2013/06/15&#39;
    GROUP  BY m.bookingid
    ORDER  BY d.priority DESC,
           m.bookingid ASC

  [1]: http://en.wikipedia.org/wiki/ADO.NET_Entity_Framework


LINQ to SQL multiple tables left outer join

I am  extremely new to MySQL and am running it on Windows. I am trying to restore a Database from a dumpfile in MySQL, but I get the following error:

    $ &gt;mysql -u root -p -h localhost -D database -o &lt; dump.sql
    ERROR: ASCII &#39;\0&#39; appeared in the statement, but this is not allowed unless option --binary-mode is enabled and mysql is run in non-interactive mode. Set --binary-mode to 1 if ASCII &#39;\0&#39; is expected. Query: &#39;SQLite format 3&#39;.

I have tried putting `--binary-mode` in the ini file but it still gives the same error. What should I do? Please help. 

**UPDATE**

As suggested by Nick in his comment I tried `$ &gt; mysql -u root -p -h localhost -D database --binary-mode -o &lt; dump.sql` but it gave me the following `ERROR at line 1: Unknown command &#39;\☻&#39;.` 
It is a 500 Mb dump file, and when I view its contents using gVIM, all I can see is expressions and data which is not comprehensible. 

Enable binary mode while restoring a Database from an SQL dump

I&#39;m trying to sum up Customer balances using the following query:

    select sum(balance) from mytable where customer = &#39;john&#39; 

However, if the customer has no balance (i.e. no matching rows in the `mytable` table), my query returns null and not 0. What&#39;s the problem?



My Select SUM query returns null. It should return 0

I have a database that was exported with pg_dump, but now when I&#39;m trying to import it again with:

    psql -d databasename &lt; mydump.sql

It fails trying to grant roles to people that don&#39;t exist. (error says &#39;Role &quot;xxx&quot; does not exist&#39;) 

Is there a way to import and set all the roles automatically to my user?

Import postgres database without roles

I have a query in `SQL`, I have to get a date in a format of `dd/mm/yy` 

Example: `25/jun/2013`. 

How can I `convert` it for `SQL server`?

Convert Date format into DD/MMM/YYYY format in SQL Server

Depending on the use case, how do I  constrain the number of files that dropzone.js will allow?

For example, I might need to only allow 1, 2, or 4 files uploaded.

It&#39;s not `uploadMultiple`. Unfortunately, `uploadMultiple` only applies to the number of files handled per request.

How to limit the number of dropzone.js files uploaded?

My queries get very slow when I add a `limit 1`.
  
I have a table `object_values`  with timestamped values for objects:

     timestamp |  objectID |  value
    --------------------------------
     2014-01-27|       234 | ksghdf

Per object I want to get the latest value:

    SELECT * FROM object_values WHERE (objectID = 53708) ORDER BY timestamp DESC LIMIT 1;
(I cancelled the query after more than 10 minutes)

This query is very slow when there are no values for a given objectID (it is fast if there are results).
If I remove the limit it tells me nearly instantaneous that there are no results:

    SELECT * FROM object_values WHERE (objectID = 53708) ORDER BY timestamp DESC;  
    ...  
    Time: 0.463 ms

An explain shows me that the query without limit uses the index, where as the query with `limit 1` does not make use of the index:

**Slow query:**


    explain SELECT * FROM object_values WHERE (objectID = 53708) ORDER BY timestamp DESC limit 1;  
    QUERY PLAN`
    ----------------------------------------------------------------------------------------------------------------------------
    Limit  (cost=0.00..2350.44 rows=1 width=126)
    -&gt;  Index Scan Backward using object_values_timestamp on object_values  (cost=0.00..3995743.59 rows=1700 width=126)
         Filter: (objectID = 53708)`

**Fast query:**

    explain SELECT * FROM object_values WHERE (objectID = 53708) ORDER BY timestamp DESC;
                                                      QUERY PLAN
    --------------------------------------------------------------------------------------------------------------
     Sort  (cost=6540.86..6545.11 rows=1700 width=126)
       Sort Key: timestamp
       -&gt;  Index Scan using object_values_objectID on working_hours_t  (cost=0.00..6449.65 rows=1700 width=126)
             Index Cond: (objectID = 53708)

The table contains 44,884,559 rows and 66,762 distinct objectIDs.  
I have separate indexes on both fields: `timestamp` and `objectID`.  
I have done a `vacuum analyze` on the table and I have reindexed the table.



Additionally the slow query becomes fast when I set the limit to 3 or higher:

    explain SELECT * FROM object_values WHERE (objectID = 53708) ORDER BY timestamp DESC limit 3;
                                                         QUERY PLAN
    --------------------------------------------------------------------------------------------------------------------
     Limit  (cost=6471.62..6471.63 rows=3 width=126)
       -&gt;  Sort  (cost=6471.62..6475.87 rows=1700 width=126)
             Sort Key: timestamp
             -&gt;  Index Scan using object_values_objectID on object_values  (cost=0.00..6449.65 rows=1700 width=126)
                   Index Cond: (objectID = 53708)

In general I assume it has to do with the planner making wrong assumptions about the exectution costs and therefore chooses for a slower execution plan.

Is this the real reason? Is there a solution for this?

PostgreSQL query very slow with limit 1

Currently `ulimit -n` shows `10000`. I want to increase it to `40000`. I&#39;ve edited &quot;/etc/sysctl.conf&quot; and put `fs.file-max=40000`. I&#39;ve also edited `/etc/security/limits.conf` and updated hard and soft values. But still ulimit shows `10000`. After making all these changes I rebooted my laptop. I&#39;ve access to root password.

    usr_name@usr_name-lap:/etc$ /sbin/sysctl fs.file-max
    fs.file-max = 500000

Added following lines in `/etc/security/limits.conf` -

    *     soft    nofile          40000
    *     hard    nofile          40000

I also added following line in `/etc/pam.d/su`-

    session&#160;&#160;&#160; required&#160;&#160; pam_limits.so

I&#39;ve tried every possible way as given on other forums, but I can reach up to a maximum limit of `10000`, not beyond that. What can be the issue?

I&#39;m making this change because `neo4j` throws maximum open file limits reached error.

How to increase Neo4j&#39;s maximum file open limit (ulimit) in Ubuntu?

Can someone please tell us/me if the [MAX_PATH issue](https://stackoverflow.com/questions/1880321/why-does-the-260-character-path-length-limit-exist-in-windows) still exists in (the technical preview of) Windows 10. And if it exists: How many characters can a path and an individual file name have?

Does MAX_PATH issue still exists in Windows 10

For pagination purposes, I need a run a query with the `LIMIT` and `OFFSET` clauses. But I also need a count of the number of rows that would be returned by that query without the `LIMIT` and `OFFSET` clauses.

I want to run:

    SELECT * FROM table WHERE /* whatever */ ORDER BY col1 LIMIT ? OFFSET ?

And:

    SELECT COUNT(*) FROM table WHERE /* whatever */

At the same time.  Is there a way to do that, particularly a way that lets Postgres optimize it, so that it&#39;s faster than running both individually?

Content Type	Original Author	Original Content on Stackoverflow
Question	Lee	View Question on Stackoverflow
Solution 1 - Mysql	Fabio	View Answer on Stackoverflow

MySQL COUNT with LIMIT

Mysql Problem Overview

Mysql Solutions

Solution 1 - Mysql

When does DynamoDB throttle request?

httpd Server not started: (13)Permission denied: make_sock: could not bind to address [::]:88

Attributions