What is an RDBMS?

An RDBMS (Relational Database Management System) is a type of database management system that stores data in a structured format, using rows and columns. Each table in an RDBMS represents a specific entity, and the relationships between these tables are maintained through keys.

Using MySQL with PHP

1. Connecting to MySQL with PHP

To interact with a MySQL database using PHP, you first need to establish a connection. You can use either the mysqli or PDO extension. Here’s how to do it with both:

Using mysqli:

<?php
$servername = "localhost";
$username = "root";
$password = "";
$database = "mydatabase";

// Create connection
$conn = new mysqli($servername, $username, $password, $database);

// Check connection
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}
echo "Connected successfully";
?>

Using PDO:

<?php
$servername = "localhost";
$username = "root";
$password = "";
$database = "mydatabase";

try {
    $conn = new PDO("mysql:host=$servername;dbname=$database", $username, $password);
    // Set the PDO error mode to exception
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    echo "Connected successfully";
} catch (PDOException $e) {
    echo "Connection failed: " . $e->getMessage();
}
?>

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2. Creating a Database and Table

To create a database and table, you can use SQL commands. Here’s an example of how to do this with PHP:

Creating a Database:

<?php
$servername = "localhost";
$username = "root";
$password = "";

// Create connection
$conn = new mysqli($servername, $username, $password);

// Create database
$sql = "CREATE DATABASE mydatabase";
if ($conn->query($sql) === TRUE) {
    echo "Database created successfully";
} else {
    echo "Error creating database: " . $conn->error;
}

// Close connection
$conn->close();
?>

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Creating a Table:

<?php
$servername = "localhost";
$username = "root";
$password = "";
$database = "mydatabase";

// Create connection
$conn = new mysqli($servername, $username, $password, $database);

// SQL to create table
$sql = "CREATE TABLE Users (
    id INT(6) UNSIGNED AUTO_INCREMENT PRIMARY KEY,
    firstname VARCHAR(30) NOT NULL,
    lastname VARCHAR(30) NOT NULL,
    email VARCHAR(50),
    reg_date TIMESTAMP
)";

if ($conn->query($sql) === TRUE) {
    echo "Table Users created successfully";
} else {
    echo "Error creating table: " . $conn->error;
}

// Close connection
$conn->close();
?>

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3. Inserting Data into a Table

To insert data into a table, use the INSERT INTO SQL statement:

<?php
$servername = "localhost";
$username = "root";
$password = "";
$database = "mydatabase";

// Create connection
$conn = new mysqli($servername, $username, $password, $database);

// SQL to insert data
$sql = "INSERT INTO Users (firstname, lastname, email)
VALUES ('John', 'Doe', '[email protected]')";

if ($conn->query($sql) === TRUE) {
    echo "New record created successfully";
} else {
    echo "Error: " . $sql . "<br>" . $conn->error;
}

// Close connection
$conn->close();
?>

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4. Retrieving Data from a Table

To retrieve data, use the SELECT SQL statement.

Using mysqli:

<?php
$servername = "localhost";
$username = "root";
$password = "";
$database = "mydatabase";

// Create connection
$conn = new mysqli($servername, $username, $password, $database);

// SQL to select data
$sql = "SELECT id, firstname, lastname, email FROM Users";
$result = $conn->query($sql);

if ($result->num_rows > 0) {
    // Output data of each row
    while($row = $result->fetch_assoc()) {
        echo "id: " . $row["id"]. " - Name: " . $row["firstname"]. " " . $row["lastname"]. " - Email: " . $row["email"]. "<br>";
    }
} else {
    echo "0 results";
}

// Close connection
$conn->close();
?>

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5. Updating and Deleting Data

You can update and delete records using the UPDATE and DELETE SQL statements:

Updating Data:

<?php
$servername = "localhost";
$username = "root";
$password = "";
$database = "mydatabase";

// Create connection
$conn = new mysqli($servername, $username, $password, $database);

// SQL to update data
$sql = "UPDATE Users SET lastname='Smith' WHERE id=1";

if ($conn->query($sql) === TRUE) {
    echo "Record updated successfully";
} else {
    echo "Error updating record: " . $conn->error;
}

// Close connection
$conn->close();
?>

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Deleting Data:

<?php
$servername = "localhost";
$username = "root";
$password = "";
$database = "mydatabase";

// Create connection
$conn = new mysqli($servername, $username, $password, $database);

// SQL to delete data
$sql = "DELETE FROM Users WHERE id=1";

if ($conn->query($sql) === TRUE) {
    echo "Record deleted successfully";
} else {
    echo "Error deleting record: " . $conn->error;
}

// Close connection
$conn->close();
?>

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