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Articles on Trending Technologies
Technical articles with clear explanations and examples
How to check if a MySQL database exists?
The schema_name command is used to check if a MySQL database exists or not. The syntax of this command is as follows −select schema_name from information_schema.schemata where schema_name = 'database name';Now, the above command is used to check whether the database exists or not. The query for that is as follows −Case 1 − The database exists.mysql> select schema_name from information_schema.schemata where schema_name = 'business'; The output obtained is as follows −+-------------+ | SCHEMA_NAME | +-------------+ | business | +-------------+ 1 row in set (0.00 sec)Case 2 − The database does not exist.mysql> select schema_name from information_schema.schemata ...
Read MoreApplying a CSS style to an ID element when the beginning of its name stays identical and the end varies in HTML
Posts can be selected using div with ‘id=post’. This will select all div elements with an id which contains a value in quotes.We can use either −div[id*='post-'] { ... } or div[id^='post-'] { ... }.div[id*='post-'] { ... } will select all div elements with id which is having all values in quotes.Or we can use,div[id^='post-'] { ... }This will select all div elements with an id which started with quotes.
Read MoreShorthand property to set columns with CSS
Use the columns property to set columns with CSS. You can try to run the following code to implement the columns property:ExampleLive Demo .demo { column-rule-color: gray; columns: 100px 4; column-rule-style: dashed; } This is demo text. This is demo text. This is demo text. This is demo text. ...
Read MoreWhat are start angle and end angle of arc in HTML5 canvas?
The arc() function has the following definition that shows the usage of start and ends angle −arc(x, y, radius, startAngle, endAngle, anticlockwise)This method has the following parameters −x and y are coordinates of the circle’s center.Radius is the circle radiusStartAngle and EndAngle define the start and endpoints of the arc in radians. Starting and closing angles are measured from the horizontal i.e. x-axisAnticlockwise is the Boolean value which when true draws arc anticlockwise otherwise in a clockwise direction.
Read MoreGetting values from HTML5 Canvas to JavaScript
When we draw anything on Canvas, it keeps no memory of anything that was drawn. While drawing we need to keep track of all the necessary information yourself as we draw. Therefore, it is not feasible to get value from HTML5 canvas to JavaScript as it keeps no memory. It just draws like this −On adding a function for button and clicking on it, you won’t be able to get what you want − You will not be able to get those values from the canvas since the canvas is just a bitmap.
Read MoreGenerating sound on the fly with JavaScript/ HTML5
The Web Audio API is used to control audio, which allows you to choose audio sources. You can also add effects; create audio visualizations, panning, etc.ExampleYou can try to run the following code snippet to generate sound −// use one context per document. Here we are creating one context for one document. You can create for other documents also var context = new (window.AudioContext || window.webkitAudioContext)(); // oscillator var os = context.createOscillator(); os.type = 'sine'; // sine is the default. So you can also use square, saw tooth, triangle os.frequency.value = 500; // setting the frequency Hz os.connect(context.destination); ...
Read MoreHow do I see all foreign keys to a table column?
To see all the foreign keys to a table or column, the referenced_column_name command is used.First, two tables are created and then related with the help of the foreign key constraint.Creating the first table −mysql> CREATE table ForeignTable -> ( -> id int, -> name varchar(200), -> Fk_pk int -> ); Query OK, 0 rows affected (0.43 sec)After creating the first table successfully, the second table is created as follows −mysql> CREATE table primaryTable1 -> ( -> Fk_pk int, -> DeptName varchar(200), -> Primary key(Fk_pk) -> ); Query OK, 0 rows affected (0.48 sec)Now, both the tables are related with ...
Read MoreDoes HTML5 allow you to interact with local client files from within a browser?
HTML5 allows us to interact with local client files (local client files are the files that are locally stored in the user’s computer). This is possible because HTML5 provides powerful APIs (Application Programming Interfaces) which are the interfaces with the help of which binary data and user’s local file system can be accessed. With the help of these file APIs, web applications can read files, file directory, can drag and drop from desktop to browser.The following are the APIs that are used to access local client files −File System APIFile APIFile Writer APIThe following are some examples −With the help ...
Read MoreHow can I add video to site background in HTML 5?
Add a button to play or pause the video. Then we have styled the video to a hundred percentage height and width so that it covers the entire background.The following is the code snippet to set video as a site background in HTML5. Your browser does not support HTML5 video. The following is to pause the video −function display() { if (video.paused) { video.play(); btn.innerHTML = "Pause the video!"; } else { video.pause(); btn.innerHTML = "Play"; } }
Read MoreHow to change max_allowed_packet size in MySQL?
The max_allowed_packet size is a session variable and is also a read only variable.To check what is the present value of max_allowed_packet, the command show variables is used. It is given as follows −mysql> show variables like 'max_allowed_packet';The following is the output+--------------------+---------+ | Variable_name | Value | +--------------------+---------+ | max_allowed_packet | 4194304 | +--------------------+---------+ 1 row in set (0.04 sec)The value of the max_allowed_packet can be changed in the ‘my.ini’ file on the client side. The query for that is given as follows −max_allowed_packet = 4567890; Now, the value can be changed globally ...
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