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SQL – An introduction to Keys

by: Caleb Jonasson - May 23rd, 2010   Filed under: SQL Add Comment

The Primary Key

Cells inside of your database are all located through an X-axis and a Y-axis. The X-axis is a row and the Y-axis is the column. Because the information inside of a database is stored downward as you go through the table each added record needs a unique identifier to be found. This is where the primary key comes in.

For every table in your database a unique ID is required to find the records and because of this every table has exactly one Primary Key. Without a primary key there would be no way to reference the information stored inside of that row and data would become inaccessible very quickly. This is also the reason why the primary key cannot have the value of “null.”

In a table there can never two of the same key. Two keys would conflict with each other and return bad records, which is why it is impossible to have this. Generally when working on a database you never want to modify the key after it has been created. This would change how the data is accessed and would be a bad idea when it comes to referencing the information should anything go wrong. There are two different kinds of keys. The first kind is a simple key and which is made of one column. The second kind of key is a composite key, which is made of 2 or more columns.

In most cases the Primary key is an integer. This allows simple ordering and counting of records on system however there are cases where a hex number can be used or even a pattern of numbers and letters.

For example, say that we were creating a database for items in a store. Each item has a unique SKU but this is something can change over time so we would still need our primary key to be a number that is completely unique. The naming also will not work for a unique ID due to name changes or the same product name with a change in SKU, which happens over time with different versions and packaging.

Foreign Keys

Foreign keys are used to reference objects or rows from other tables. Theses keys generally reference parent tables from child tables and are used to cross data between tables. This means that the table with the foreign key is always going to be the child in the link.

Unlike the primary key, the foreign key can have a null value, which leads to no link being made between the two tables for that object. These keys also do not need to be unique; in fact they often never are unique do to the nature of how they are used.

An example of the foreign key, continuing from the example used in primary keys, will require us to add another column to the initial table so we will now have ID, SKU, and Vendor. The tables will look like this.

As you can see, in this example we have the foreign key doubling as a primary key in the lower table, which is used in as a vendor in the top table. This is a quick and simple way to store the values easily in the database and comes in handy when working with relationships.

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Creating multiple sidebar menus in wordpress

by: Caleb Jonasson - May 22nd, 2010   Filed under: php, Web Development 2 Comments

In this tutorial I won’t just be making a sidebar menu, but three additional menus that will be placed side by side in the footer. Unfortunately the code for this is not as easy as it may seem. The possibility of creating the sidebars through only your footer.php and sidebar.php is not going to happen. Fortunately the code is very simple and involves a lot of copy and pasting with a couple modifications.

For this tutorial I will be using wordpress 2.9.2 (currently the latest release)

When creating multiple “sidebars” You only need to do two things. The first thing is to edit the functions.php page, and the second is to edit the HTML where the sidebar/dynamic menu will be placed.

The first thing that we will be doing is opening our functions.php page. The code for one sidebar should look like this:

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if ( function_exists('register_sidebar_widget') ){
    register_sidebar(array(
        'name'=> __('Sidebar', 'cwj'),
        'id' => 'normal_sidebar',
        'before_widget' => '<li id="%1$s" class="widget %2$s">',
        'after_widget' => '</li>',
        'before_title' => '<h2 class="widgettitle">',
        'after_title' => '</h2>',
    ));
}

The next thing we will need to do is modify this code so we can have four dynamic menus throughout our WordPress theme. We will need to copy and paste the array and change out the name and the ID to something new and exciting. Because the menus will be placed in my footer I will be calling them “Footer1″ etc for each menu. The ID can be anything as long as it is unique to that specific menu. If you have two menus with the same ID you will only be able to add widgets to the last referenced menu.

The code should now look something like this:

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if ( function_exists('register_sidebar_widget') ){
    register_sidebar(array(
        'name'=> __('Sidebar', 'CJDesign-dark1'),
        'id' => 'normal_sidebar',
        'before_widget' => '<li id="%1$s" class="widget %2$s">',
        'after_widget' => '</li>',
        'before_title' => '<h2 class="widgettitle">',
        'after_title' => '</h2>',
    ));
    register_sidebar(array(
        'name'=> __('Footer1', 'CJDesign-dark1'),
        'id' => 'col_sidebar1',
        'before_widget' => '<li id="%1$s" class="widget %2$s">',
        'after_widget' => '</li>',
        'before_title' => '<h2 class="widgettitle">',
        'after_title' => '</h2>',
    ));
    register_sidebar(array(
        'name'=> __('Footer2', 'CJDesign-dark1'),
        'id' => 'col_sidebar2',
        'before_widget' => '<li id="%1$s" class="widget %2$s">',
        'after_widget' => '</li>',
        'before_title' => '<h2 class="widgettitle">',
        'after_title' => '</h2>',
    ));
    register_sidebar(array(
        'name'=> __('Footer3', 'CJDesign-dark1'),
        'id' => 'col_sidebar3',
        'before_widget' => '<li id="%1$s" class="widget %2$s">',
        'after_widget' => '</li>',
        'before_title' => '<h2 class="widgettitle">',
        'after_title' => '</h2>',
    ));
}

The next stage in this tutorial is to quickly and easily insert the line of code to display your newly created dynamic menus. Just place this into the HTML where you would like it to be.

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<?php if ( !function_exists('dynamic_sidebar') || !dynamic_sidebar('Footer3') ) : ?>
<?php endif; ?>

You simply need to replace where I have Footer3 with the name of the sidebar that you previously created with the function.

The sidebar now looks as follows:

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<div class="footer-col">
	<ul>
		<?php if ( !function_exists('dynamic_sidebar') || !dynamic_sidebar('Footer1') ) : ?>
  		<?php endif; ?>
    </ul>
</div>
<div class="footer-col">
	<ul>
		<?php if ( !function_exists('dynamic_sidebar') || !dynamic_sidebar('Footer2') ) : ?>
        <?php endif; ?>
    </ul>
</div>
<div class="footer-col">
	<ul>
		<?php if ( !function_exists('dynamic_sidebar') || !dynamic_sidebar('Footer3') ) : ?>
        <?php endif; ?>
    </ul>
</div>

And the widgets can be modified through the WordPress widget page.

<img>

And the final product.

<img>

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Recycle pages by splitting your website into pieces with PHP

by: Caleb Jonasson - May 18th, 2010   Filed under: php, video 3 Comments

Recycle pages by splitting your website into pieces with PHP from Calebj on Vimeo.

Edit: Tuesday December 28th 2010, 9:11pm

I have just uploaded the archived end result at a comments request. You can download it here: Recycle_pages_code_with_design.zip

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Remove images and increase load times with CSS3

by: Caleb Jonasson - May 5th, 2010   Filed under: CSS, Web Development Add Comment

Recently when working on a clients site I found that there were a lot of images being used when a quick little CSS fix could have done the trick. The basic outline of the site involved a few transparencies and a lot of drop shadows. The drop shadows were placed on the container/wrap and the text had drop shadows that had been all done in Photoshop. (Some of the drop shadows were not consistent.)

After looking at the site I told the client that within three minutes I could remove all of the images being for text, drop shadows and opacity allowing his site to load faster.

The answer was what I had expected and the following code was quickly being thrown into the site.

The Code

For the drop shadows on divs:

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.container{
     width:1080px;
     margin:0 auto;
     -moz-border-radius:5px;
     -webkit-border-radius:5px;
     -moz-box-shadow: 0 2px 5px #666;
     -webkit-box-shadow: 0 2px 5px #666;
}

For the drop shadows on text:

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h3{
	font-family: Times;
	letter-spacing: 1px;
	text-shadow: 2px 2px 2px #000;
}

For the opacity:

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.sidebar ul{
	list-style-type:none;
	opacity: 0.9;
	width: 180px;
}
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