In what situations would a LEFT JOIN be preferred over other types of SQL joins when working with PHP and MySQL?

A LEFT JOIN is preferred over other types of SQL joins when you want to retrieve all records from the left table (table1) and only matching records from the right table (table2). This is useful when you want to display all records from the left table, even if there are no corresponding records in the right table. 

<?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

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

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

$sql = "SELECT table1.column1, table2.column2
        FROM table1
        LEFT JOIN table2 ON table1.id = table2.id";

$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"]. "<br>";
  }
} else {
  echo "0 results";
}

$conn->close();
?>

Keywords

PHP MySQL LEFT JOIN SQL joins data retrieval

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