Happy Easter

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Relational databases: some simple rules (part 2)

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This is the second part of the two parts article "Relational databases: some simple rules".

In the first part we have seen the ideas of tables and the way we can relate them.
And now... the conclusion!

Primary and foreign keys
We now need to move on a bit, but please keep in mind the example made in the first part of the article: two tables, with a relation for the state column.
The names table has the following columns: ID, name, surname, address, post code, city, state.
The states table has the following columns: ID, state.
In the persons table, the “state” column will contain only IDs related to the states table.
The ID column in the person table is a primary key. The ID in the state table is a primary key.
The “state” column in the persons table is a foreign key.
Quite easy, isn’t it?

Relational databases: some simple rules (part 1)

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It doesn't matter what we prefer to use, either Ms Access or SQL Server or Oracle, or even MySql, but when we want to create a new database, we really need to consider its structure, plan it and finally create all the database elements.
To do such a thing might seem easy – and in general it is – but a good development plan is what we need to avoid pitfalls and future issues with the structure of the database. The complexity of a database is surely one of the things to be considered, in fact it is clear that a more complex database will surely be more complex to develop.
Some simple rules can be taken into account and in this two parts article we are going to see some important points we need to keep in mind when planning a new database.

CSS3: border-image

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With CSS3 we can use images as border of an element. Apart from using the normal border styles already available in CSS, we can now make our web pages more colourful and attractive (if you really like colours and shapes!).
Just to go directly to the core, we can use the following style for, let's say, all divs in a document:

div
{
-webkit-border-image:url(myborder.png) 30 30 round;
-o-border-image:url(myborder.png) 30 30 round;
border-image:url(myborder.png) 30 30 round;
}

The border-image property is in fact a shorthand property. As you can see from the above example, we are using different values which are:
1) border-image-source which is the path to our image;
2) border-image-slice which is the inward offsets of the image;
3) border-image-width which is the widths of the image;
4) border-image-outset which defines the portion of the image that goes beyond the box;
5) border-image-repeat which sets the way the image will be repeated.

ASP: conditional statements with If...Then...Else...ElseIf

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In ASP we can use conditional statements in different ways. The basic syntax we are used to, is If ... Then ... Else ... End, however we will see that there are some interesting things about it.

First of all let's consider a simple conditional statement in ASP. As you already know, we do not use any brackets or parenthesis. A basic example could be:

<%
Dim numVar
numVar = 5
If numVar = 5 then
  response.write("The variable numVar is 5")
End if
%>

HTML5: geolocation

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With HTML5 is now possible to use the target browser in order to determine the location from which the user is accessing the web. It is not, as you may understand, a GPS location (unless the user is surfing from a GPS capable device), but it can be quite interesting in some cases where special services are supplied on a web page.

How can we develop a geolocation service on our web page?

Well, first of all try and see the final effect: go here and enjoy. After that, please get back on the web thought...

First of all let me say that all location services on the target browser must be granted by the user. As you may have noticed by visiting the above live example, the browser has asked you permission for the use of location services (unless you've granted permanent access to your location).

CSS: cursor

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As you surely already know we can change the cursor type using CSS.
They way we do it is very simple. It is enough to use the cursor property and apply it to any element in our web page:

<style>
.myDiv {
   cursor: crosshair;
}
</style>
<div class="myDiv">The cursor here has a crosshair shape</div>

What are the different option we have?
The answer after the break :-)

HTML5: telephone numbers on web pages

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Every day on TV we hear news saying that most of the people in the world is surfing the web using a mobile device. You are probably reading this very article with your iPhone or Galaxy, or maybe using your favourite tablet.
As many of the above mobile devices are actually capable of making phone calls, we can insert telephone numbers on web page and make them clickable, so that any mobile user will be able to use the link to call the shown number.

SQL Server: compare tables

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When we import, export or synchronise tables, it's a hard job if we have many records.
In the past, I've found some difficulties when I need to compare two tables in SQL Server.
The tables contained different records and I needed to consolidate them in the first table.
The first thing I wanted to do was to actually see which were the differences: I needed a list of records in order to understand the situation.
I've found a good solution for that, and let me say, a quite unexpected solution indeed.