Annu Sehrawat (Backend-Senior Associate Consultant L1 - Development)

Database

A database is an organized collection of data. It is the gathering of schemes, tables, queries, reports, views, and other objects.

Relational Database

A relational database consists of a set of tables that stores particular Sets of data.

Creating a database

Create a new Database and therefore the file used to store the database.

Syntax:-

database_name:- database_name is often a maximum of 128 characters. Unless a logical name isn’t specified for the log file. If a logical log file name isn’t specified, SQL Server generates the logical_file_name and therefore the os_file_name for the log by appending a suffix to database_name. This limits database_name to 123 characters in order that the generated logical file name is not any quite 128 characters.

Creating a database that specifies data and transaction log files.

Drop database

Remove one or more user Databases from an Instance of SQL Server.

Syntax:-

database_name:- Specifies the name of the database to be removed. To display an inventory of databases, use the sys.databases catalog view.

Dropping multiple databases:

Alter database

Modifies a database, or the files and filegroups related to the database. Adds or removes filegroups from a database and modifies the elements of a database or its files and filegroups, changes the database collation, and sets database options.

Syntax:-

OldDatabase_Name:- Is that the name of the database to be modified?

MODIFY NAME:- Renames the database with the name specified as New Database_Name.

Example:

Data Definition Language (DDL)

Data Definition Language (DDL) is a vocabulary wont to define data structures in SQL Server. Use the following statements to create, alter, or drop data structures in an instance of SQL Server.

Create Command

Create command is additionally used to create a table. We can define names and data types of various columns along.

Syntax:-

RenameCommand

Rename command is employed to rename a table.

Syntax:-

AlterCommand:

• To add a column to an existing table.

Syntax:-

• To modify an existing column.

Syntax:-

• To rename the column.

Syntax:-

• Alter is additionally used to drop a column.

Syntax:- 

Drop Command:

The Drop query completely removes a table from databases.

Syntax:-

Truncate Command:

The Truncate command removes all records from a table. But this command will not demolish the table's structure

Syntax:-

Data Manipulation Language (DML)

Data Manipulation Language (DML) is a vocabulary wont to retrieve and work with data in SQL Server. Use the following statements to add, modify, query, or remove data from a SQL Server database.

Insert Command:

Insert command is employed to insert data into a table.

Syntax:-

Example: A table student with the following fields.

Insert a record into the student table.

Update Command:

The Update command is employed to update a row of a table.

Syntax:-

Delete Command:

Delete command is used to delete the data from a table. Delete command can also be used with the condition to delete a specific row.

Syntax:-

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Sass is an extension to css initially designed by Hampton Catlin and developed by Natalie Weizenbaum in 2006. After its initial versions, Weizenbaum and Chris Eppstein have extended the Sass scripting language used in Sass files. Sass is completely free to download and use .Sass is a CSS pre-processor scripting language that is interpreted or compiled into Cascading Style Sheets (CSS).Sass is compatible with all versions of the css. Sass helps to reduce the repetition of css and saves time. Sass is a stable and powerful CSS extension language that styles the document structurally.

Sass file has .scss extension.

Sass uses Indentation.

Why Use Sass ?

Css stylesheets were getting lager, more complex and harder to maintain. This is where Sass can help. It has features which don't exist in CSS like variables, operators, expressions, nested rules, mixins, imports, inheritance, built-in functions, and other stuff.

Let's take an example explaining why Sass is useful

Suppose our website has three main colors #2f80c2, #e66d70 and #6c757d. So, what percentage times one got to type those HEX values? A LOT of times. And what about variations of the same colors?

Instead of typing the above hex values a lot of times, you can use Sass and write like this:

So, when using Sass, and the primary color changes everywhere, you only need to change it in one place.

How does Sass Works ?

A Web browser doesn’t understand Sass code. So we need a Sass pre-processor to convert Sass code into standard CSS. This process is called Translating. We give some Sass code to the translator and then get some CSS code back.

Sass Variables 

Variables are used to store information that can be re-use whenever needed throughout the stylesheet.

Variables start with a dollar ($) sign followed by a variable name and variable assignment is done with colon (:)

Sass Variable Syntax:  $variable_name: value;

Data types Sass supports :- Numbers, Strings, Colors and Booleans.

Example to show use of Sass variables :- 

Sass Code

After translating to CSS code output looks Like :- 

Output CSS Code

Some Sass Features :- 

1. Import :- Just like CSS, Sass also uses @import directive to import files.

Sass Import Syntax :

@import filename;

2. Mixin :- @mixin directive used to create CSS code that can be used throughout the stylesheet.

Sass mixin Syntax :

@mixin name {

  property: value;

  property: value;

  ...

}

The @include directive is used to include(use) the mixins.

Sass @include mixin Syntax:

selector {

  @include mixin-name;

}

3. Extend :- @extend directive is used to share a set of CSS properties from one selector to another.

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Comments On Dynamically Created Pages in Wordpress

Wordpress provides a default comments table i.e (wp_comments) to store comments on its post, pages and also we can store comments of custom post type but sometimes if we have a requirement to store comments on the dynamically created page.

For Eg:- If I have a page with a custom template in Wordpress. With the actual page content (like header and footer) which is similar for all dynamically created pages, we also show the dynamically created pages content which is different for all pages and differentiated via passed in URL variables.

Suppose I created a page called Blogs in WordPress and assigned it to my ‘blog.php’ template. Users can hit the page at https://mywebsite.com/blogs 

They can also go to https://mywebsite.com/blogs/what-is-ML/ and the page template reads in the “blog URL” via our get_query_var(‘blog_url’) and it shows blog content for just that blog.

Here's what our requirement is to add comments to the "specific blog" which is not an actual page inside WordPress, but are created on the basis of “blog URL”.

We can add comments_template() to the page, but the comments_template() is based on page id or post id. So if we add a comment on one blog then, it will also show on all blogs because all blogs have the same page id.

For eg:- If we post a comment on https://mywebsite.com/blogs/what-is-ML/ then it will also show on https://mywebsite.com/blogs/what-is-AI/ but we don’t want to show comments on https://mywebsite.com/blogs/what-is-ML/ to show up on https://mywebsite.com/blogs/what-is-AI/ and vice-versa.

There are 2 ways to do that, one is to customize the wp_comments table and add a new unique field but I don’t think it’s a good idea to mess up with the main functionality of wordpress. Second one is to create your own custom table (e.g wp_custom_comments) having the same structure as the default wp_comments table but with your extra fields.

You can write a function in your function.php file to create a custom comments table like this :-

function custom_comments_table()

{

global $wpdb;

$table_name = $wpdb->prefix. "custom_comments";

$charset_collate = $wpdb->get_charset_collate();

if( $wpdb->get_var("SHOW TABLES LIKE '" . $table_name . "'") !=  $table_name)

{

$sql = "CREATE TABLE `$table_name` (

 `comment_ID` bigint(20) UNSIGNED NOT NULL AUTO_INCREMENT,

 `comment_post_ID` bigint(20) UNSIGNED NOT NULL DEFAULT 0,

 `comment_author` tinytext CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL,

 `comment_author_email` varchar(100) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL DEFAULT '',

 `comment_author_url` varchar(200) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL DEFAULT '',

 `comment_author_IP` varchar(100) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL DEFAULT '',

 `comment_date` datetime NOT NULL DEFAULT '0000-00-00 00:00:00',

 `comment_date_gmt` datetime NOT NULL DEFAULT '0000-00-00 00:00:00',

 `comment_content` text CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL,

 `comment_karma` int(11) NOT NULL DEFAULT 0,

 `comment_approved` varchar(20) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL DEFAULT '1',

 `comment_agent` varchar(255) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL DEFAULT '',

 `comment_type` varchar(20) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL DEFAULT '',

 `comment_parent` bigint(20) UNSIGNED NOT NULL DEFAULT 0,

 `user_id` bigint(20) UNSIGNED NOT NULL DEFAULT 0,

/* here you can add your own custom fields*/

 PRIMARY KEY (`comment_ID`))$charset_collate;";

}

require_once(ABSPATH . 'wp-admin/includes/upgrade.php');

dbDelta($sql);

}

add_action('init','custom_comments_table');

Once the table is created successfully, you can store your comments on dynamically created pages and can also show that data in the wordpress admin panel using ‘WP_List_Table’ class.