How can the use of * in SQL queries affect the outcome when fetching data in PHP?

Using * in SQL queries can fetch all columns from a table, which can be inefficient and may return unnecessary data. It is recommended to specify the exact columns needed in the SELECT statement to improve performance and reduce the amount of data transferred. By explicitly listing the columns, you can fetch only the necessary data and optimize the query. 

<?php
// Connect to the database
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "database";
$conn = new mysqli($servername, $username, $password, $dbname);

// Fetch data from the database with specified columns
$sql = "SELECT column1, column2 FROM table_name";
$result = $conn->query($sql);

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

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

Keywords

PHP SQL queries data fetching wildcard character query optimization

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