How can the use of "SELECT *" in MySQL queries impact the performance and security of a PHP application?

Using "SELECT *" in MySQL queries can impact performance negatively because it retrieves all columns from a table, even those that are not needed. This can result in unnecessary data transfer between the database server and the application, leading to slower query execution times. Additionally, using "SELECT *" can also pose a security risk as it exposes all columns in a table, potentially revealing sensitive information to unauthorized users. To address this issue, it is recommended to explicitly list the columns you need in your SELECT statement rather than using "SELECT *". This approach not only improves performance by fetching only the necessary data but also enhances security by limiting the exposure of sensitive information. 

<?php
// Connect to the database
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

$conn = new mysqli($servername, $username, $password, $dbname);

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

// Select specific columns instead of using "SELECT *"
$sql = "SELECT column1, column2, column3 FROM myTable";
$result = $conn->query($sql);

if ($result->num_rows > 0) {
    // Output data of each row
    while($row = $result->fetch_assoc()) {
        echo "Column1: " . $row["column1"]. " - Column2: " . $row["column2"]. " - Column3: " . $row["column3"]. "<br>";
    }
} else {
    echo "0 results";
}

$conn->close();
?>

Keywords

SELECT * MySQL queries performance security PHP application

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