learnings

create table Users(
    rollno int(20) NOT NULL,
    rname varchar(20) NOT NULL,
    lname varchar(20) NOT NULL,
    dob date NOT NULL,
    gyear int(4) NOT NULL,
    password 
    
    );

    "ALTER TABLE `users` ADD PRIMARY KEY(`rollno`);

"ALTER TABLE `users` drop `rollno`;

how to set a clomn to auto_increment?

    ALTER TABLE `adminpass` CHANGE `sno` `sno` INT(11) NOT NULL AUTO_INCREMENT, add PRIMARY KEY (`sno`);


admin will alter details shown on the students page
admin can send updates regarding something to only that students it wants to send via his portal
ex. links, and other details

students can update their queries

$a = "hello";
$b = "yellow";
//concat two strings
$res = $a.$b;


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<!-- SELECT * FROM `placementdb`.`users` WHERE rollno='1814310124' AND password='e3a034574a737501fa579850ffe9b139'; -->

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SELECT *
FROM `placementdb`.`users`
FULL OUTER JOIN `placementdb`.`companydata`
ON `placementdb`.`users`.rollno = `placementdb`.`companydata`.rollno;

SELECT *
FROM users
FULL OUTER JOIN companydata
ON users.rollno = companydata.rollno;

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every refresh should have session start t conitnue with the session!!

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inline php shpuld contain '' 
ex:
<div style="text-align: center;">
        <h1><?php echo "$name";?></h1>

    </div>

    ==========

CREATE TABLE `placementdb`.`updates` (`sno` INT NOT NULL AUTO_INCREMENT , `companyname` VARCHAR(1000) NOT NULL , `pkg` FLOAT NOT NULL , `lastdate` DATE NOT NULL , `maxpkg` FLOAT NOT NULL , `comment` TEXT NULL DEFAULT NULL , PRIMARY KEY (`sno`)) ENGINE = InnoDB; 

============
$details = mysqli_fetch_array($res); 
                echo "{$details[0]}";  // when fetching single things use indexes than column's Name
======      

echo "<p>Updates for you!</p>";
                // require_once "dbcon.php";
                $rollno = $_SESSION['rollno'];
                echo "$rollno";
                $sql = "SELECT max(distinct(pkg)) from companydata where rollno='$rollno'";
                $res = mysqli_query($conn,$sql);
                $count = mysqli_num_rows($res);

                $details = mysqli_fetch_array($res); 
                if($details[0]) {
                    
                    // echo "{$details[0]}";  // when fetching single things use indexes than column's Name
                    $mx = $details[0]+0.0;
                    $s = "SELECT * from `placementdb`.`updates` WHERE maxpkg=$mx";
                    $r = mysqli_query($conn,$s);
                    $c = mysqli_num_rows($r);
                    if($c>0){
                        while($details2 = mysqli_fetch_array($r)){
                        echo"<p>{$details2['comment']}</p>";
                        echo"<a href='{$details2['links']}'>{$details2['links']}</a>";
                        echo"<br><br>";
                        }
                    }
                    
                }
============

session_destroy();  //if session is not started what will happen.. to session_destroy()
            header("location:index.php");

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