What is CRUD? Basic Database Operations Explained for Beginners

1. Basic Operations (CRUD)

·         INSERT (Data add karne ke liye)

·         SELECT (Data show/fetch karne ke liye)

·         UPDATE (Data edit/change karne ke liye)

·         DELETE (Data remove karne ke liye)

2. Filters & Conditions

·         WHERE (Specific data filter karne ke liye)

·         AND (Dono condition match karne ke liye)

·         OR (Koi ek condition match karne ke liye)

·         IN (Multiple fixed options me se filter karne ke liye)

·         BETWEEN (Price ya Date ki range filter karne ke liye)

3. Search & Sorting

·         LIKE (Website search bar me matching words dhoodne ke liye)

·         ORDER BY (A to Z ya Low to High sort karne ke liye)

·         ASC (Ascending/Chhote se bada sort)

·         DESC (Descending/Bade se chhota sort)

4. Limits & Pages (Pagination)

·         LIMIT (Ek page par kitna data dikhana hai)

·         OFFSET / SKIP (Agla page dikhane ke liye purana data skip karna)

5. Calculations & Groups

·         COUNT (Total items ginn ne ke liye)

·         SUM (Total price/amount jodna)

·         AVG (Average nikalna)

·         GROUP BY (Category ke hisab se data group karna)

·         HAVING (Grouped data par filter lagana)

6. Tables Linking

·         JOIN (Do alag-alag tables ka data ek sath jod kar dikhana)

·         UNION (Do alag queries ke results ko ek sath milana)

 

 

dbconnection.php

<?php

$con=mysqli_connect("localhost", "root", "", "crm");

if(mysqli_connect_errno()){

echo "Connection Fail".mysqli_connect_error();

}

?>

Registration.php

<?php

session_start();

error_reporting(0);

include("dbconnection.php");

if(isset($_POST['submit']))

{

  $name=$_POST['name'];

  $email=$_POST['email'];

  $password=$_POST['password'];

  $mobile=$_POST['phone'];

  $gender=$_POST['gender'];

  $query=mysqli_query($con,"select email from user where email='$email'");

  $num=mysqli_fetch_array($query);

  if($num>1)

  {

  echo "<script>alert('Email-id already register with us. Please try with diffrent email id.');</script>";

  echo "<script>window.location.href='registration.php'</script>";

  }

  else

  {

 mysqli_query($con,"insert into user(name,email,password,mobile,gender) values('$name','$email','$password','$mobile','$gender')");

echo "<script>alert('Successfully register with us. Now you can login');</script>"; 

echo "<script>window.location.href='login.php'</script>";

}

  }

?>

Admin page login to go php

1. Session aur Error Handling

PHP

session_start();

error_reporting(0);

include("dbconnection.php");

• session_start(); : Yeh website par session shuru karta hai. Iska kaam yeh yaad rakhna hai ki kaun sa user login hua hai, taaki jab tak wo browser band na kare ya logout na ho, tab tak website use yaad rakhe.
• error_reporting(0); : Yeh website par aane wale kisi bhi error (galti) ko screen par dikhne se rokta hai, taaki user ko koi ajeeb code ya warning na dikhe (security ke liye bhi accha hai).
• include("dbconnection.php"); : Yeh aapki database wali file ko is page se jodta hai, taaki hum database se baat kar sakein.

2. Login Button Trigger Check

PHP

if(isset($_POST['login']))

{

• if(isset($_POST['login'])) : Yeh check karta hai ki kya user ne login form ka "Login" button dabaya hai? Agar haan, toh hi iske andar ka code chalega.

3. Database mein Check Karna (SELECT Query)

PHP

$ret=mysqli_query($con,"SELECT * FROM admin WHERE name='".$_POST['email']."' and password='".$_POST['password']."'");

$num=mysqli_fetch_array($ret);

• mysqli_query(...) : Yeh database mein ek sawaal (Query) bhejta hai.
• SELECT * FROM admin WHERE... : Yeh database ke admin table mein check karta hai ki kya koi aisa admin hai jiska name aur password wahi hai jo user ne form mein dala hai.
• mysqli_fetch_array($ret); : Agar match mil jata hai, toh yeh us admin ka saara data nikal kar $num naam ke variable mein rakh deta hai.

⚠️ Zaroori Note (Security Warning): Is code mein ek bohot badi galti hai—isme $ _POST ka data bina safe kiye seedhe query mein dala gaya hai. Is wajah se isme SQL Injection ka khatra hai (koi bhi hacker isko aasani se hack kar sakta hai). Isko hamesha mysqli_real_escape_string() ya Prepared Statements se safe banana chahiye.

4. Agar Login Kamyab (Success) Raha toh:

PHP

if($num>0)

{

$extra="home.php";

$_SESSION['alogin']=$_POST['email'];

$_SESSION['id']=$num['id'];

echo "<script>window.location.href='".$extra."'</script>";

exit();

}

• if($num>0) : Agar database mein sahi admin mil gaya (matlab value 0 se zyada hai):
• $_SESSION['alogin'] = ... aur $_SESSION['id'] = ... : Yeh admin ka email aur id session mein save kar leta hai. Iska fayda yeh hota hai ki ab home.php page ko pata chal jayega ki kaun sa admin login hua hai.
• window.location.href='home.php' : Yeh JavaScript ka use karke user ko automatic home.php (Dashboard) page par bhej (redirect kar) deta hai.

5. Agar Username ya Password Galat (Fail) Raha toh:

PHP

else

{

$_SESSION['action1']="*Invalid username or password";

$extra="index.php";

 

echo "<script>window.location.href='".$extra."'</script>";

exit();

}

}

• else : Agar database mein details match nahi huin:
• $_SESSION['action1'] = "*Invalid..." : Yeh ek error message session mein save kar deta hai taaki login page par dikhaya ja sake ki password galat hai.
• window.location.href='index.php' : Yeh user ko wapas index.php (Login Page) par hi bhej deta hai taaki wo fir se koshish kar sake.

================================================================

Chaliye in charo operations (CRUD) ko HTML form ke sath pure syntax, code aur Hindi meaning ke sath samajhte hain.

1. INSERT (Data Add Karne Ke Liye)

Jab user form mein data bharega aur submit karega, tabhi data insert hoga.

HTML Form Code:

HTML

<form action="insert.php" method="POST">
    <label>Naam Likhein:</label>
    <input type="text" name="user_name" required>
    
    <label>Email Likhein:</label>
    <input type="email" name="user_email" required>
    
    <button type="submit" name="submit_btn">Save Karein</button>
</form>

• action="insert.php": Iska matlab hai ki jab user button dabayega, toh form ka data insert.php naam ki file ke paas jayega.

• method="POST": Yeh data ko chupakar (safely) doosre page par bhejta hai.

• name="user_name": Yeh PHP ke liye ek pehchan (ID) hai taaki PHP ko pata chale ki kis box ka data uthana hai.

PHP Back-end Code (insert.php):

PHP

<?php
include("dbconnection.php"); // Database se judne ke liye

if(isset($_POST['submit_btn'])) {
    $name = $_POST['user_name']; // HTML ke input ka data nikalna
    $email = $_POST['user_email'];

    // SQL Query data insert karne ke liye
    $query = "INSERT INTO users (name, email) VALUES ('$name', '$email')";
    mysqli_query($con, $query);
}
?>

2. SELECT (Data Show/Fetch Karne Ke Liye)

Isme hume HTML mein koi form nahi chahiye hota, balki hum PHP se data lakar HTML ki Table mein dikhate hain.

HTML aur PHP Code:

PHP

<table border="1">
    <tr>
        <th>ID</th>
        <th>Naam</th>
        <th>Email</th>
    </tr>

    <?php
    include("dbconnection.php");
    
    // Database se sabhi users ka data mangwana
    $query = "SELECT * FROM users";
    $result = mysqli_query($con, $query);

    // loop chalakar ek-ek karke saara data table ke rows (<tr>) mein dikhana
    while($row = mysqli_fetch_array($result)) {
        echo "<tr>";
        echo "<td>" . $row['id'] . "</td>";
        echo "<td>" . $row['name'] . "</td>";
        echo "<td>" . $row['email'] . "</td>";
        echo "</tr>";
    }
    ?>
</table>

• while($row = ...): Jab tak database mein data milta rahega, yeh loop chalta rahega aur HTML ki table mein nayi lines (<tr>) banti rahengi.

• $row['name']: Yeh database ke column ka naam hai jiska data screen par dikhana hai.

3. UPDATE (Data Edit/Change Karne Ke Liye)

Isme hume ek aisa form chahiye hota hai jisme purana data pehle se bhara hua ho, taaki user use badal sake.

HTML Form Code:

HTML

<form action="update.php" method="POST">
    <input type="hidden" name="user_id" value="1"> 
    
    <label>Naya Naam:</label>
    <input type="text" name="new_name" value="Rahul Kumar">
    
    <button type="submit" name="update_btn">Update Karein</button>
</form>

• type="hidden": Yeh user ko screen par nahi dikhta, par isse PHP ko pata chalta hai ki kis ID wale records ko badalna hai.

• value="Rahul Kumar": Yahan purana naam pehle se dikhega jise user edit karega.

PHP Back-end Code (update.php):

PHP

<?php
include("dbconnection.php");

if(isset($_POST['update_btn'])) {
    $id = $_POST['user_id'];
    $name = $_POST['new_name'];

    // UPDATE query jo sirf usi ID ka naam badlegi
    $query = "UPDATE users SET name='$name' WHERE id='$id'";
    mysqli_query($con, $query);
}
?>

4. DELETE (Data Remove Karne Ke Liye)

Data delete karne ke liye aksar hum HTML mein ek chhota sa form ya fir ek direct link (button) banate hain jisme user ki ID judi hoti hai.

HTML Form Code:

HTML

<form action="delete.php" method="POST">
    <input type="hidden" name="user_id" value="1">
    
    <button type="submit" name="delete_btn" onclick="return confirm('Kya aap sach mein delete karna chahte hain?')">
        Delete Karein
    </button>
</form>

• onclick="return confirm(...)": Yeh JavaScript ka ek pop-up dikhayega taaki galti se kisi ka data delete na ho jaye.

PHP Back-end Code (delete.php):

PHP

<?php
include("dbconnection.php");

if(isset($_POST['delete_btn'])) {
    $id = $_POST['user_id'];

    // DELETE query jo specified ID ko database se uda degi
    $query = "DELETE FROM users WHERE id='$id'";
    mysqli_query($con, $query);
}
?>

Ek Line Mein Samajhie (Summary)

• INSERT: HTML Form se data liya ➡️ PHP ne INSERT query se database mein daal diya.

• SELECT: PHP ne SELECT query se data nikala ➡️ HTML Table ke andar fit karke dikha diya.

• UPDATE: HTML Form mein naya data liya ➡️ PHP ne WHERE laga kar database mein badal diya.

• DELETE: HTML Button se ID bheji ➡️ PHP ne DELETE WHERE lagakar use gayab kar diya.

 =====================================================================

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What is CRUD? Basic Database Operations Explained for Beginners php 1

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SQL Filters & Conditions Tutorial: WHERE, AND, OR, IN, BETWEEN Explained php 2

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