External Style Sheets

Introduction :

External style sheets have many powerful that make them ubiquitous in professional Web sites:

• It keeps your website design and content separate.
• It's much easier to reuse your CSS code if you have it in a separate file. Instead of typing the same CSS code on every web page you have, simply have many pages refer to a single CSS file with the "link" tag.
• You can make drastic changes to your web pages with just a few changes in a single CSS file.
• It allows a single style sheet to control the rendering of multiple documents.
• This results in a time-savings for the author, a savings of space for the web server, and less download time for the user.
• This method can be used in both HTML and XML.
• In Application When using CSS it is preferable to keep the CSS separate from your HTML.
• Placing CSS in a separate file allows the web designer to completely differentiate between content (HTML) and design(CSS).

An External Style Sheet is a file containing only CSS syntax and should carry a MIME type of "text/css."

It is saved with a ".css" filename extensions that file is then referenced in your HTML using the "link" instead of "style".

By using the Link Tag to load a basic external style sheet (CSS), it's possible to control the look n feel of multiply WebPages by making changes to One style sheet.

This means that it is easy to change font, bgcolor, background, etc on ALL pages - just by changing one external style sheet (CSS).

Those CSS files define page attributes for every page to which they are linked.

The style information is not explicitly tied directly to the document's elements, so Selector syntax is used to specify what styles attach to which portions of the document tree.

The full range of CSS syntax is allowed in this method.

Example with codes :

The 'link' is always added to the Head Section i.e anywhere between the "head" and the "/head"

HTML Code:

    link rel="stylesheet" type="text/css" href="style.css"

Just create a text (ASCII) file named (test.css) that contains the code shown below.

Put the style.css file in the same folder / directory as the file .

Let us create an external CSS file. Open up notepad.exe, or any other plain text editor and type the following CSS code.

CSS Code:

    body
    {
        background-color: #FFFFF0;
        font-family: Arial, Verdana, sans-serif;
        font-size: 18px;
        color: #00008B;
    }

    a
    {
        font-family: Arial, Verdana, sans-serif;
        font-size: 18px;
        color: Blue;
        text-decoration: underline;
    }

    a:hover
    {
        font-family: Arial, Verdana, sans-serif;
        font-size: 18px;
        color: Red;
        background-color: Green;
    }

    h1 
    { 
        font-family: Arial, Verdana, sans-serif; 
        font-size: 32px; 
        color: blue; 
    }

    table
    {
        font-family: Arial, Verdana, sans-serif;
        font-size: 18px;
        color: #00008B;
        margin-top: 0px;
        margin-right: 0px;
        margin-bottom: 0px;
        margin-left: 0px;
        padding-top: 0px;
        padding-right: 0px;
        padding-bottom: 0px;
        padding-left: 0px;
    }

Now save the file as a CSS (test.css) file.

Now create a new HTML file and fill it with the following code.

HTML Code:

    link rel="stylesheet" type="text/css" href="test.css"

Then save this file as "Sample.html" (without the quotes) in the same directory as your CSS file.

Now open your HTML file in your web browser and it should look something like this..

Display:

A Blue Header

Image link in Blue Colour. then on Mouse hover it will be red colur with green background because we changed it with CSS!

Advantages :

External style sheets have many powerful that make them ubiquitous in professional Web sites:

• It keeps your website design and content separate.
• It's much easier to reuse your CSS code if you have it in a separate file. Instead of typing the same CSS code on every web page you have, simply have many pages refer to a single CSS file with the "link" tag.
• You can make drastic changes to your web pages with just a few changes in a single CSS file.
• It allows a single style sheet to control the rendering of multiple documents.This results in a time-savings for the author, a savings of space for the web server, and less download time for the user.
• This method can be used in both HTML and XML.

SET Vs. SELECT in SQL Server

Introduction

SET and SELECT both key words are used to Assign Variables in SQL Server.

SET and SELECT both specifies the columns to be changed and the new values for the columns.

The values in the specified columns are updated with the values specified in the SET and SELECT in all rows that match the WHERE clause search condition.

If no WHERE clause is specified, all rows are updated.

There are some difference based on the Performance, Process like Follows :

1. SET is the ANSI standard for variable assignment, SELECT is not.

2. SELECT can be used to assign values to more than one variable at a time, Whereas SET allows to assign data to only one variable at a time.

Example :

    /* Declaring variables */
    DECLARE @Var1 AS int, @Var2 AS int

    /* The same can be done using SET, but two SET statements are needed */
    SET @Var1 = 1
    SET @Var2 = 2

    /* Initializing two variables at once */
    SELECT @Var1 = 1, @Var2 = 2

But use SET instead SELECT, for variable initialization, It will throw the following error

Example :

    SET @Var1 = 1, @Var2 = 2

    Msg 102, Level 15, State 1, Line 10
    Incorrect syntax near ','.

3. When assigning from a query if there is no value returned then SET will assign NULL, where SELECT will not make the assignment at all .so the variable will not be changed from it's previous value.

Example :

Run it in master Database in SQL Server.

    /* Returns NULL */
    DECLARE @Title varchar(80)
    --SET @Title = 'Not Found'

    SET @Title =
    (
    SELECT error
    FROM SysMessages
    WHERE Description = 'Invalid Description'
    )

    SELECT @Title
    GO

    /* Returns the string literal 'Not Found' */
    DECLARE @Title varchar(80)
    SET @Title = 'Not Found'

    SELECT @Title = error
    FROM SysMessages
    WHERE Description = 'Invalid Description'

    SELECT @Title
    GO

4. Let using a query needs to populate a variable and the Query returns more than one value.

SET will fail with an error in this scenario.

But SELECT will assign one of the returned rows and mask the fact that the query returned more than one row.

As a result, bugs in your the could go unnoticed with SELECT, and this type of bugs is hard to track down too.

Example :

    /* Consider the following table with two rows */
    SET NOCOUNT ON
    CREATE TABLE #Table (i int, j varchar(10))
    INSERT INTO #Table (i, j) VALUES (1, 'Sunday')
    INSERT INTO #Table (i, j) VALUES (1, 'Monday')
    GO

    /* Following SELECT will return two rows, but the variable gets its value from one of those rows, without an error.
    you will never know that two rows existed for the condition, WHERE i = 1 */
    DECLARE @j varchar(10)
    SELECT @j = j FROM #Table WHERE i = 1
    SELECT @j
    GO

    /* If you rewrite the same query, but use SET instead, for variable initialization, you will see the following error */
    DECLARE @j varchar(10)
    SET @j = (SELECT j FROM #Table WHERE i = 1)
    SELECT @j

    Msg 512, Level 16, State 1, Line 4
    Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression.

Based on the above results, when using a query to populate variables, we should always use SET.

If you want to be sure that only one row is returned then only use SELECT, as shown below:

Example :

    DECLARE @j varchar(10)
    SELECT @j = (SELECT j FROM #Table WHERE i = 1)
    SELECT @j

5. This very feature of SELECT makes it a winner over SET, when assigning values to multiple variables. A single SELECT statement assigning values to 3 different variables, is much faster than 3 different SET statements assigning values to 3 different variables.

In this scenario, using a SELECT is at least twice as fast, compared to SET.

So, the conclusion is, if there is a loop in th stored procedure that manipulates the values of several variables, and if you want to squeeze as much performance as possible out of this loop, then do all variable manipulations in one single SELECT statement or group the related variables into few SELECT statements as show below:

Example :

    SELECT @Var1 = @Var1 + 1, @Var2 = @Var2 - 1, @CNT = @CNT + 1