I think you&#39;re looking for: `SELECT a, b, COUNT(a) FROM tbl GROUP BY a, b`

    SELECT group,subGroup,COUNT(*) FROM tablename GROUP BY group,subgroup

You must group both columns, group and sub-group, then use the aggregate function `COUNT()`.

    SELECT
      group, subgroup, COUNT(*)
    FROM
      groups
    GROUP BY
      group, subgroup

I am using Org-mode in Emacs to handle all my technical documentation. I would like to use Emacs to prepare questions that I have for Stack Overflow. Is there an Emacs mode for that, or even better, an extension for Org-mode to handle Stack Overflow formatting? Ideally it should include all formatting options supported by the markdown syntax used in the Stack Overflow question/comment buffers.

Emacs mode for Stack Overflow&#39;s markdown

I have a buffer with some binary data:

    var b = new Buffer ([0x00, 0x01, 0x02]);

and I want to append `0x03`.

How can I append more binary data? I&#39;m searching in the documentation but for appending data it must be a string, if not, an error occurs (*TypeError: Argument must be a string*):

    var b = new Buffer (256);
    b.write (&quot;hola&quot;);
    console.log (b.toString (&quot;utf8&quot;, 0, 4)); //hola
    b.write (&quot;, adios&quot;, 4);
    console.log (b.toString (&quot;utf8&quot;, 0, 11)); //hola, adios

Then, the only solution I can see here is to create a new buffer for every appended binary data and copy it to the major buffer with the correct offset:

    var b = new Buffer (4); //4 for having a nice printed buffer, but the size will be 16KB
    new Buffer ([0x00, 0x01, 0x02]).copy (b);
    console.log (b); //&lt;Buffer 00 01 02 00&gt;
    new Buffer ([0x03]).copy (b, 3);
    console.log (b); //&lt;Buffer 00 01 02 03&gt;

But this seems a bit inefficient because I have to instantiate a new buffer for every append.

Do you know a better way for appending binary data?


  [1]: https://github.com/Gagle/Node-BufferedWriter
  [2]: https://github.com/Gagle/Node-BufferedReader


**EDIT**

I&#39;ve written a [BufferedWriter][1] that writes bytes to a file using internal buffers. Same as [BufferedReader][2] but for writing.

A quick example:

    //The BufferedWriter truncates the file because append == false
    new BufferedWriter (&quot;file&quot;)
    	.on (&quot;error&quot;, function (error){
    		console.log (error);
    	})
    	
    	//From the beginning of the file:
    	.write ([0x00, 0x01, 0x02], 0, 3) //Writes 0x00, 0x01, 0x02
    	.write (new Buffer ([0x03, 0x04]), 1, 1) //Writes 0x04
    	.write (0x05) //Writes 0x05
    	.close (); //Closes the writer. A flush is implicitly done.
    
    //The BufferedWriter appends content to the end of the file because append == true
    new BufferedWriter (&quot;file&quot;, true)
    	.on (&quot;error&quot;, function (error){
    		console.log (error);
    	})
    	
    	//From the end of the file:
    	.write (0xFF) //Writes 0xFF
    	.close (); //Closes the writer. A flush is implicitly done.
    
    //The file contains: 0x00, 0x01, 0x02, 0x04, 0x05, 0xFF

**LAST UPDATE**

Use [concat](http://nodejs.org/api/buffer.html#buffer_class_method_buffer_concat_list_totallength).

How to append binary data to a buffer in node.js

I have a table in my mysql db that has two columns: group and subgroup. See below.   

     group, subGroup
     grp-A, sub-A
     grp-A, sub-A
     grp-A, sub-B      
     grp-B, sub-A
     grp-B, sub-B
     grp-B, sub-B
I am trying to get the number of records for each unique couple group/subGroup.

This is what I expect:

    group, subGroup, count
    grp-A, sub-A, 2
    grp-A, sub-B, 1
    grp-B, sub-A, 1
    grp-B, sub-B, 2

After reading some posts I tried several sql queries using group by, count(), but I do not manage to get the expected result. How can I fix this?

Using group by on two fields and count in SQL

I have a table in my mysql db that has two columns: group and subgroup. See below.
<pre><code class="hljs language-css"> group, subGroup
 grp-A, sub-A
 grp-A, sub-A
 grp-A, sub-B 
 grp-B, sub-A
 grp-B, sub-B
 grp-B, sub-B
</code></pre>
I am trying to get the number of records for each unique couple group/subGroup.
This is what I expect:
<pre><code class="hljs language-css">group, subGroup, count
grp-A, sub-A, 2
grp-A, sub-B, 1
grp-B, sub-A, 1
grp-B, sub-B, 2
</code></pre>
After reading some posts I tried several sql queries using group by, count(), but I do not manage to get the expected result. How can I fix this?

I have recently noticed that my `wp_options` table seems to be a bit large. It contains 1161 rows, and is about 2.1mb in size.

I have installed [Clean Options][1]. It looks like development stopped on the plugin back in 2010, but it still did the job.

I now have a long list of potentially orphaned entries. Is there an easy way to go about sorting these, and figuring out which to remove and which to keep? Also, could this be responsible for causing performance issues with the website?

Thank you for reading, any ideas are welcomed!

**Update**: The Clean Options plugin returned some transients in the list, which lead me to find out that there are several hundred transient files in the `wp_options` table.  There are a whole bunch that look like: 

 - `_site_transient_browser_5728a0f1503de54634b3716638...` 
 - `_site_transient_timeout_browser_03df11ec4fda7630a5...`
 - `_transient_feed_83dcaee0f69f63186d51bf9a4...`
 - `_transient_plugin_slugs`
 - `_transient_timeout_feed_83dcaee0f69f63186d51bf9a4b...`

and so on.  Like I said, there are several hundred rows that take look like this.  Is it safe to just dump them?

Thanks

 


  [1]: http://wordpress.org/extend/plugins/clean-options/

Can I remove transients in the wp_options table of my WordPress install?

I get this error when I try to source a large SQL file (a big `INSERT` query).

    mysql&gt;  source file.sql
    ERROR 2006 (HY000): MySQL server has gone away
    No connection. Trying to reconnect...
    Connection id:    2
    Current database: *** NONE ***
    
    ERROR 2006 (HY000): MySQL server has gone away
    No connection. Trying to reconnect...
    Connection id:    3
    Current database: *** NONE ***

Nothing in the table is updated.  I&#39;ve tried deleting and undeleting the table/database, as well as restarting MySQL.  None of these things resolve the problem.

Here is my max-packet size:

    +--------------------+---------+
    | Variable_name      | Value   |
    +--------------------+---------+
    | max_allowed_packet | 1048576 |
    +--------------------+---------+

Here is the file size:

    $ ls -s file.sql 
    79512 file.sql

When I try the other method...

    $ ./mysql -u root -p my_db &lt; file.sql
    Enter password: 
    ERROR 2006 (HY000) at line 1: MySQL server has gone away

ERROR 2006 (HY000): MySQL server has gone away

In a SQL statement, how do I compare a date saved as TIMESTAMP with a date in YYYY-MM-DD format?

Ex.: `SELECT * FROM table WHERE timestamp = &#39;2012-05-25&#39;`

I want this query returns all rows having timestamp in the specified day, but it returns only rows having midnight timestamp.

thanks


How to compare timestamp dates with date-only parameter in MySQL?

How do I count columns of a table

I&#39;m just about to write a query that includes a `WHERE isok=1`. As the name implies, `isok` is a boolean field (actually a `TINYINT(1) UNSIGNED` that is set to 0 or 1 as needed).

Is there any performance gain in indexing this field? Would the engine (InnoDB in this case) perform better or worse looking up the index?

Is there any performance gain in indexing a boolean field?

I want to close the existing connections to an MS SQL Server so that I can do a restore on that database programatically.

How to close existing connections to a DB

Is there a way to use the `Now()` function in SQL to select values with today&#39;s date? 

I was under the impression `Now()` would contain the time as well as date, but today&#39;s date would have the time set to `00:00:00` and therefore this would never match?

Comparing results with today&#39;s date?

I&#39;ve been tasked with coming up with a means of translating the following data:

    date        category        amount
    1/1/2012    ABC             1000.00
    2/1/2012    DEF             500.00
    2/1/2012    GHI             800.00
    2/10/2012   DEF             700.00
    3/1/2012    ABC             1100.00

into the following:

    date        ABC             DEF             GHI
    1/1/2012    1000.00
    2/1/2012                    500.00
    2/1/2012                                    800.00
    2/10/2012                   700.00
    3/1/2012    1100.00

The blank spots can be NULLs or blanks, either is fine, and the categories would need to be dynamic. Another possible caveat to this is that we&#39;ll be running the query in a limited capacity, which means temp tables are out. I&#39;ve tried to research and have landed on `PIVOT` but as I&#39;ve never used that before I really don&#39;t understand it, despite my best efforts to figure it out. Can anyone point me in the right direction?

SQL Server dynamic PIVOT query?

How to pass table valued parameter to stored procedure using ADO.NET?

Pass table valued parameter using ADO.NET

How do you rewrite expressions containing the standard `IS DISTINCT FROM` and `IS NOT DISTINCT FROM` operators in the SQL implementation in Microsoft SQL Server 2008R2 that does not support them?

Content Type	Original Author	Original Content on Stackoverflow
Question	Marc	View Question on Stackoverflow
Solution 1 - Mysql	Corbin	View Answer on Stackoverflow
Solution 2 - Mysql	user1127214	View Answer on Stackoverflow
Solution 3 - Mysql	farzane	View Answer on Stackoverflow

Using group by on two fields and count in SQL

Mysql Problem Overview

Mysql Solutions

Solution 1 - Mysql

Solution 2 - Mysql

Solution 3 - Mysql

How to append binary data to a buffer in node.js

Emacs mode for Stack Overflow's markdown

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