What are the potential pitfalls of using INNER JOIN in PHP when dealing with multiple tables and potentially missing entries?

When using INNER JOIN in PHP to query multiple tables, one potential pitfall is that it will only return rows where there is a match in all tables involved. This means that if there are missing entries in one of the tables, those rows will not be included in the result set. To address this issue, you can use LEFT JOIN instead, which will return all rows from the left table (the first table in the query) and the matched rows from the right table. 

<?php
// Establish a connection to the database
$pdo = new PDO('mysql:host=localhost;dbname=your_database', 'username', 'password');

// Query using LEFT JOIN to retrieve all rows from the first table and matching rows from the second table
$sql = "SELECT * FROM table1 LEFT JOIN table2 ON table1.id = table2.table1_id";
$stmt = $pdo->query($sql);

// Fetch and display the results
while ($row = $stmt->fetch(PDO::FETCH_ASSOC)) {
    echo $row['column1'] . ' - ' . $row['column2'] . '<br>';
}
?>

Keywords

INNER JOIN PHP multiple tables missing entries potential pitfalls

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