Whats is SQL and What's the difference between PL/SQL and SQL?
Full form of SQL is Structured Query Language. It is used for Querying and manipulating the Database. Difference between SQL and PL/SQL: 1 -> Sql is a query language that is used to query(select/create/insert/update/delete) the database. But PL/SQL is completely a programming language just like php and java. 2-> SQL is data oriented language. But PL/SQL is used to create the application because its a procedural language. 3-> In SQL we can execute one statement at a time. But in PL/SQL we can execute block of statements. 4-> We can embed SQL in PL/SQL but vice-versa is not true.
What is PHP and what is superglobals variables in PHP?
PHP is stands for Hypertext Processor. It's a server side scripting language and it is used to design the dynamic web pages or website. Superglobals Variables: There are several variables in PHP that are called Superglobals variables because they can be access from anywhere in php script. They can be accessed within/from the methods, Superglobals variables are below: $_REQUEST :- This variable is used to collect the data from a html form submitted from Browser/client. It holds all the form fields data. It could be any form field like textbox, checkbox, selectbox, radio button etc. $_POST: POST is also collect the data from HTML form just like $_REQUEST. But it holds the data that is submitted using POST method of form. $_GET: GET is also collect the data from HTML form just like $_REQUEST. But it holds the data that is submitted using GET method of form. It also holds the data passed in URL as URL param. $_FILES: It used to hold the uploaded file data submitted in HTML form using input box of "file" type. Also, note that HTML form must have the attribute set as: enctype="multipart/form-data" . $_ENV: It is used to holds the environment variables returned from the web server. Lets say if we store some key/value in $_ENV variable than we can access it in Client side within php tags (i.e. <?php ?>). $_COOKIE: It holds Cookie information stored at client side. cookie is the small text files stored at client browser. $_SERVER: It holds the information the path of the current script, script location and headers etc. $_SESSION: It is an associative array that hols the session information of current session of user/client. $GLOBALS: This variable is used to access global variables from anywhere in the php script. This variable stores all the variables declared globally in php script in the form of associative array. Where array index represent the variable name and value is the variable value. <?php $GLOBALS['xyz'] = 22; echo $xyz; // it will print 22 ?>
What do you mean by Java is platform independent?
Java Program is first compiled into Byte Code. Byte Code is not a native machine code. The byte code only understood by JVM (Java Virtual Machine). JVM is java's run time environment. It interpret the Byte code into the Native Machine code that is binary code that is understood by Operating System. So this way Java Code can be written and complied on any Operating system and can be run on any other operating system. The other Operating System must need JVM to run that complied code called Byte code (i.e. .class file). The most important thing is that while JAVA is platform independent language but JVM is platform-dependent. Different JVM is required/designed for different Operating systems and then byte code is able to run on different platforms.