How can PHP developers effectively query and retrieve data from multiple tables within a single database using PHP and MySQLi?

To effectively query and retrieve data from multiple tables within a single database using PHP and MySQLi, developers can use SQL JOIN statements to combine data from different tables based on a related column. By specifying the columns to select and the tables to join in the SQL query, developers can fetch data from multiple tables in a single query. 

<?php
// Establish a connection to the database
$connection = new mysqli("localhost", "username", "password", "database");

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

// SQL query to retrieve data from multiple tables using JOIN
$sql = "SELECT table1.column1, table2.column2
        FROM table1
        JOIN table2 ON table1.common_column = table2.common_column";

// Execute the query and fetch the results
$result = $connection->query($sql);

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

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

Keywords

PHP MySQLi database query retrieve

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