SQL

Introduction

What is SQL?

• SQL stands for Structured Query Language

      you can access and manipulate(build) the database.

What Can SQL do?

SQL can execute queries against a database
SQL can retrieve data from a database
SQL can insert records in a database
SQL can update records in a database
SQL can delete records from a database
SQL can create new databases
SQL can create new tables in a database
SQL can create stored procedures in a database
SQL can create views in a database
SQL can set permissions on tables, procedures, and views

Database Tables

A database most often contains one or more tables. Each table is identified by a name (e.g. "Student" or "Employee"). Tables contain records (rows) with data.

>rows are also know as tuples.


 Student ID     Student name     contact     age
1                       Ash                    890          21
2                      Anny                  789           22
3                      Stain                   465           20
4                      Harry                  769            25
5                       Dev                    899            23

Some of The Most Important SQL Commands

SELECT - extracts data from a database
UPDATE - updates data in a database
DELETE - deletes data from a database
INSERT INTO - inserts new data into a database
CREATE DATABASE - creates a new database
ALTER DATABASE - modifies a database
CREATE TABLE - creates a new table
ALTER TABLE - modifies a table
DROP TABLE - deletes a table
CREATE INDEX - creates an index
DROP INDEX - deletes an index





 

The SQL SELECT Statement :

The SELECT statement is used to select data from a database.

SQL SELECT Syntax

 

SELECT column_name,column_name
FROM table_name;

and

 

SELECT * FROM table_name;

 

Example:

 

 SELECT * FROM Student;

 

The SQL SELECT DISTINCT Statement

In a table, a column may contain many duplicate values; and sometimes you only want to list the different (distinct) values.
 

 SELECT DISTINCT column_name,column_name
FROM table_name;

 

 

Example:

select distinct Student name from Student ;

The SQL WHERE Clause 

The WHERE clause is used to extract only those records that specifies the needs .

SQL WHERE Syntax

SELECT column_name,column_name
FROM table_name
WHERE column_name operator value;

 

Example 

 

SELECT * FROM Student
WHERE name='Ash';

 

Operators in The WHERE Clause

The following operators can be used in the WHERE clause:

Operator	Description
=	Equal
<>	Not equal.
>	Greater than
<	Less than
>=	Greater than or equal
<=	Less than or equal
BETWEEN	Between an inclusive range
LIKE	Search for a pattern
IN	To specify multiple possible values for a column

 

 

 

 

Java script 7

Function Declarations

 function functionName(parameters)

 {
  code to be executed
} 

Example

function myFunction(a, b)
 {
    return a + b;
}

Function Expressions

A function expression can be stored in a variable:

Example

var x = function (a, b) {return a + b}; 

 

 

Functions Can Be Used as Values

 

Example

function myFunction(a, b)

 {
    return a + b;
}

var x = myFunction(4, 3);

 

Function Parameters and Arguments

  

functionName(parameter1, parameter2, parameter3)

 {
    code to be executed
}  

Java script 6

JavaScript Form Validation

 

If the form submitted is Empty,the function should return alert message and prevent from submitting the form.

JavaScript Example

function validateForm()

 {
    var x = document.forms["myForm"]["fname"].value;
    if (x == null || x == " ")

 {
        alert("Name must be filled out");
        return false;
    }
}

 After filling out the fname the form will be submitted. 

 

Typical validation tasks are:

• has the user filled in all required fields?
• has the user entered a valid date?
• has the user entered text in a numeric field?

End of the basic Java script.

Java script 5

JavaScript Loops

 

•  for

• while

•  do while 

  The for loop has the following syntax:

   

          for (statement 1; statement 2; statement 3)

          {
               code block to be executed
          }

 Example

for (i = 0; i < 5; i++) 

{
    text += "The number is " + i + "<br>";
}

The While Loop Syntax

while (condition) 

{
    code block to be executed
}

Example

In the following example, the code in the loop will run, over and over again, as long as a variable (i) is less than 5:

Example

while (i < 5) 

{
    text += "The number is " + i;
    i++;
}

The Do/While Loop Syntax

The do/while loop is a variant of the while loop.

do {
    code block to be executed
}
while (condition);

Example

The example below uses a do/while loop. The loop will always be executed at least once, even if the condition is false, because the code block is executed before the condition is tested:

Example

do {
    text += "The number is " + i;
    i++;
}
while (i < 10);

 

 

Java script 4

Conditional Statements 

JavaScript we have the following conditional statements:

• if

• else

• else if 

• switch 

   

  The if Statement

  Syntax

  if (condition) 

  {
      block of code to be executed if the condition is true
  } 

   

   Example : 

   <hmtl>

  <script>

  var age=20;

  if(age>18)

  {

  document.write("Qualifies for driving");

  }

  </scritp>

  </html>

  The else Statement

  if (condition)

   {
      block of code to be executed if the condition is true
  } 

  else

   {
      block of code to be executed if the condition is false
  }

   

  Example : 

   <hmtl>

  <script>

  var age=20;

  if(age>18)

  {

  document.write("Qualifies for driving");

  } 

  else

  {

  document.write("doesnt qulify for driving");

  }

  </scritp>

  </html>

  
  

  The else if Statement

  Use the else if statement to specify a new condition if the first condition is false.
  

  Syntax

  if (condition1) 

  {
      block of code to be executed if condition1 is true
  }

   else if (condition2) 

  {
      block of code to be executed if the condition1 is false and condition2 is true
  }

   else

   {
      block of code to be executed if the condition1 is false and condition2 is false
  }

   

   

  Example:Simillar to if else.
  

  The JavaScript Switch Statement

   

  Syntax 

   

   switch(expression)

   {
      case n:
          code block
          break;
      case n:
          code block
          break;
      default:
          default code block
  }

   

   

Java script 3

JavaScript Arithmetic Operators

Operator	Description
+	Addition
-	Subtraction
*	Multiplication
/	Division
%	Modulus
++	Increment
--	Decrement

 

JavaScript Assignment Operators

Operator	Example
=	x = y
+=	x += y
-=	x -= y
*=	x *= y
/=	x /= y
%=	x %= y

 

JavaScript  Logical Operators

Operator	Description
= =	equal to
= = =	equal value and equal type
!=	not equal
!==	not equal value or not equal type
>	greater than
<	less than
>=	greater than or equal to
<=	less than or equal to
?	ternary operator

 

JavaScript Function Syntax

 function name(parameter1, parameter2, parameter3)

 {
    code to be executed
} 

 

 Example:

var x = myFunction(5, 2);        // Function is called, return value will end up in x
function myFunction(a, b)

 {
    return a * b;                // Function returns the product of a and b }

 

Java script 2

JavaScript Syntax

Java script statements  are separated by semicolons (;)

Ex:

var x = 2; var y = 3; var z = x + y; 

the values (fixed) are also known as literals are written directly instead of putting them in a qoutes

20.2

03

string are written as

"Google"

"Blackfacers"

 

Variables can be assigned values using = operator :

var x;

x=50;

Arithmetic operators :
 

(5*2)+5

 The values can be of string type can also be joined using operator + like

"Black" + "  " + "facers"

Blackfacers will be the output.

Java script comments :

Code after double slashes  //  or between      /*  and  */     is treated as a comment.

  Javascript program ex:

 var x = 10;
var y =5;
var z = x + y;
document.getElementById("sample").innerHTML = z;

JavaScript Code Blocks :

JavaScript statements can be grouped together in code blocks, inside curly brackets {...}.

 function myFunction()
{
    document.getElementById("demo").innerHTML = "Hello CODERS.";
    document.getElementById("sample").innerHTML = "How are you?";
}

Here function is a keyword.