Assuming your model name is `Bar` and it has a column named `bar`, this should work:

    Bar.maximum(&quot;bar&quot;)

See the excellent [Rails Guides section on Calculations](http://guides.rubyonrails.org/active_record_querying.html#calculations) for more info.

one more way

    Bar.select(&quot;Max(bar) as max_bar&quot;).first.max_bar

I&#39;ve built a web app that uses the HTML5 &lt;video&gt; tag and JavaScript code that renders other content synchronized with the running video. It works great in desktop browsers: Firefox, Chrome, and Safari. On an iPhone or a DroidX, the native video player pops up and takes over the screen, thus obscuring the other dynamic content that I want to display simultaneously with the video.

Is there any way around this? If necessary, I&#39;ll figure out how to write native apps for both those platforms, but it would save me a ton of effort if I could just stick with HTML5/JavaScript.


Can I avoid the native fullscreen video player with HTML5 on iPhone or android?

I am playing around with HTML5 WebSockets. I was wondering, how do I close the connection gracefully? Like, what happens if user refreshes the page, or just closes the browser?

There is a weird behavior when a user just refresh the page without calling `websocket.close()` - when they return after the refresh it will hit the `websocket.onclose` event.

Closing WebSocket correctly (HTML5, Javascript)

Currently I can make the straight-up SQL query on my DB:

```sql
SELECT MAX(bar) FROM table_name
```

And it returns with the max value in that table. When I make what I consider to be an equivalent call in Rails, however, it does not work. I am calling:

```ruby
Bar.all(:select =&gt; &quot;Max(bar)&quot;)
```

This simply returns with:

```ruby    
[#&lt;Bar &gt;]
```

In the column I&#39;m calling on is a series of identifying numbers, I&#39;m looking for the largest one. Is there some other way of accessing this in Rails?



Ruby on Rails: getting the max value from a DB column

Currently I can make the straight-up SQL query on my DB:
<pre><code class="hljs language-sql">SELECT MAX(bar) FROM table_name
</code></pre>
And it returns with the max value in that table. When I make what I consider to be an equivalent call in Rails, however, it does not work. I am calling:
<pre><code class="hljs language-ini">Bar.all(:select => "Max(bar)")
</code></pre>
This simply returns with:
<pre><code class="hljs language-bash">[#&#x3C;Bar >]
</code></pre>
In the column I'm calling on is a series of identifying numbers, I'm looking for the largest one. Is there some other way of accessing this in Rails?

I have a cursor containing several columns from the row it brings back that I would like to process at once.  I notice most of the examples I&#39;ve seeing on how to use cursors show them assigning a particular column from the cursor to a scalar value one at a time, then moving to the next row, 

e.g.

    OPEN db_cursor  
    FETCH NEXT FROM db_cursor INTO @name  
    
    WHILE @@FETCH_STATUS = 0  
    BEGIN  
           --Do Stuff with @name scalar value, then get next row from cursor
    
           FETCH NEXT FROM db_cursor INTO @name  
    END

What I want to know is if it&#39;s possible to do something like the following:

        OPEN db_cursor  
        FETCH NEXT FROM db_cursor; 
        
        WHILE @@FETCH_STATUS = 0  
        BEGIN  
               SET @myName = db_cursor.name;
               SET @myAge = db_cursor.age;
               SET @myFavoriteColor = db_cursor.favoriteColor;
               --Do stuff with scalar values

               FETCH NEXT FROM db_cursor; 
        END

Help is always appreciated.

Get Multiple Values in SQL Server Cursor

I have a very basic `UPDATE SQL` -

    UPDATE HOLD_TABLE Q SET Q.TITLE = &#39;TEST&#39; WHERE Q.ID = 101;

This query runs fine in `Oracle`, `Derby`, `MySQL` - but it &lt;i&gt;fails in SQL server 2008&lt;/i&gt; 
with following error: 

&gt; &quot;Msg 102, Level 15, State 1, Line 1  Incorrect syntax near &#39;Q&#39;.&quot;

If I remove all occurrences of the alias, &quot;Q&quot; from SQL then it works.

But I need to use the alias. 

How to write UPDATE SQL with Table alias in SQL Server 2008?

I have to execute a loop in database. This is only a one time requirement.
After executing the function, I am dropping the function now.

Is there any good approach for creating temporary / disposable functions?

How to create a temporary function in PostgreSQL?

Whats the best browser tool for HSQLDB databases?

Best SQL browser for HSQLDB?

like when I do 

    SELECT [Date]
      FROM [FRIIB].[dbo].[ArchiveAnalog]
      GROUP BY [Date]

how can I specify the group period ?

MS SQL 2008

**2nd Edit**

I&#39;m trying 

    SELECT MIN([Date]) AS RecT, AVG(Value)
      FROM [FRIIB].[dbo].[ArchiveAnalog]
      GROUP BY (DATEPART(MINUTE, [Date]) / 10)
      ORDER BY RecT

changed %10 to / 10. is it possible to make Date output without milliseconds ?

How to group time by hour or by 10 minutes 

The #new_record? function determines if a record has been saved. But it is always false in the `after_save` hook. Is there a way to determine whether the record is a newly created record or an old one from update? 

I&#39;m hoping not to use another callback such as `before_create` to set a flag in the model or require another query into the db.

Any advice is appreciated. 

Edit: Need to determine it in `after_save` hook, and for my particular use case, there is no `updated_at` or `updated_on` timestamp

How to determine if a record is just created or updated in after_save

I&#39;m trying to use a different/custom layout named &quot;devise&quot; for the sign_in action. I found [this](https://github.com/plataformatec/devise/wiki/How-To:-Create-custom-layouts) page in the devise wiki, and the second example even says you can do it per-action (in this case, `sign_in` action), but it shows no example of doing that. Someone on IRC told me I could try this:

    class ApplicationController &lt; ActionController::Base
      protect_from_forgery

      layout :layout_by_resource

      def layout_by_resource
        if devise_controller? &amp;&amp; resource_name == :user &amp;&amp; action_name == &#39;sign_in&#39;
          &quot;devise&quot;
        else
          &quot;application&quot;
        end
      end
    end

But it does not seem to be working as it&#39;s still loading the default application layout. I would appreciate any help.

different layout for sign_in action in devise

I have read the documentation at http://api.rubyonrails.org/classes/ActiveRecord/Callbacks.html, but don&#39;t understand when the `around_*` callbacks are triggered in relation to `before_*` and `after_*`.

Any help much appreciated.

Thanks.

Rails: around_* callbacks

When my app runs (or when I run from commandline) the wkhtmltopdf command I get the following error: (showing it from command line)

    #&gt; wkhtmltopdf 
    wkhtmltopdf: error while loading shared libraries: libXrender.so.1: cannot open shared object file: No such file or directory

I noticed the lib is indeed in the `/usr/lib` folder but not the `/lib` folder. Does it matter which one of these it is in? Is there any way to get it to recognize it?

    #&gt; ls -l /usr/lib/libXrender.so*
    lrwxrwxrwx 1 root root    19 Feb 17 07:20 /usr/lib/libXrender.so -&gt; libXrender.so.1.3.0
    lrwxrwxrwx 1 root root    19 Feb 17 07:20 /usr/lib/libXrender.so.1 -&gt; libXrender.so.1.3.0
    -rwxr-xr-x 1 root root 39184 Jan 29  2010 /usr/lib/libXrender.so.1.3.0

    #&gt; ls -l /lib/libXrender.so*
    ls: cannot access /lib/libXrender.so*: No such file or directory

I also checked dependencies of the lib

    # ldd /usr/lib/libXrender.so.1
    	libX11.so.6 =&gt; /usr/lib/libX11.so.6 (0x00002b9cb5afd000)
    	libc.so.6 =&gt; /lib/libc.so.6 (0x00002b9cb5e04000)
    	libXau.so.6 =&gt; /usr/lib/libXau.so.6 (0x00002b9cb6143000)
    	libXdmcp.so.6 =&gt; /usr/lib/libXdmcp.so.6 (0x00002b9cb6347000)
    	libdl.so.2 =&gt; /lib/libdl.so.2 (0x00002b9cb654d000)
    	/lib64/ld-linux-x86-64.so.2 (0x0000555555554000)

This is running on an EngineYard gentoo server

Rails: Error running wkhtmltopdf -- (error while loading shared libraries)

Suppose a database contains a field &#39;keywords&#39; and sample records include:
&quot;pipe wrench&quot;
&quot;monkey wrench&quot;
&quot;crescent wrench&quot;
&quot;crescent roll&quot;
&quot;monkey bars&quot;

is there a way in activerecord to find the records where the keyword field contains the substring &quot;crescent&quot;?

(It&#39;s just a quick and dirty lookup for a quick concept prototype)



Content Type	Original Author	Original Content on Stackoverflow
Question	keybored	View Question on Stackoverflow
Solution 1 - Sql	Dylan Markow	View Answer on Stackoverflow
Solution 2 - Sql	Manish Kasera	View Answer on Stackoverflow

Ruby on Rails: getting the max value from a DB column

Sql Problem Overview

Sql Solutions

Solution 1 - Sql

Solution 2 - Sql

Closing WebSocket correctly (HTML5, Javascript)

Can I avoid the native fullscreen video player with HTML5 on iPhone or android?

Attributions