How can PHP developers avoid errors when querying data from multiple tables in a database?

When querying data from multiple tables in a database, PHP developers can avoid errors by using JOIN statements to combine the tables based on a common column. This ensures that the data retrieved is accurate and complete, without the need for multiple separate queries. Additionally, developers should always sanitize user input to prevent SQL injection attacks and handle any potential errors or exceptions that may arise during the query process. 

<?php

// Establish a database connection
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "database";

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

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

// Query data from multiple tables using a JOIN statement
$sql = "SELECT * FROM table1
        JOIN table2 ON table1.id = table2.id";

$result = $conn->query($sql);

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

$conn->close();

?>

Keywords

PHP SQL JOIN error handling database normalization

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