PHP MySQL Use The WHERE Clause

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PHP MySQL Use The WHERE Clause

The WHERE clause is used to filter records. The WHERE clause is used to extract only those records that fulfill a specified condition.

SELECT column_name(s) FROM table_name WHERE column_name operator value

First, we set up the SQL query that selects the id, firstname and lastname columns from the MyGuests table where the lastname is "Doe". The next line of code runs the query and puts the resulting data into a variable called $result.

Then, the function num_rows() checks if there are more than zero rows returned.If there are more than zero rows returned, the function fetch_assoc() puts all the results into an associative array that we can loop through. The while() loop loops through the result set and outputs the data from the id, firstname and lastname columns.

Example (MySQLi Object-oriented)

    •       
                         
<?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 id, firstname, lastname
 FROM MyGuests WHERE lastname='Doe'";
$result = $conn->query($sql);

if ($result->num_rows > 0) {
    // output data of each row
    while($row = $result->fetch_assoc()) {
    echo "id: " . $row["id"]. " - Name: " . $row["firstname"]. "
     " . $row["lastname"]. "
    ";
    }
} else {
    echo "0 results";
}
$conn->close();
?>

    Example (MySQLi Procedural)

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

// Create connection
$conn = mysqli_connect($servername, $username, $password, $dbname);
// Check connection
if (!$conn) {
    die("Connection failed: " . mysqli_connect_error());
}

$sql = "SELECT id, firstname, lastname FROM MyGuests WHERE
 lastname='Doe'";
$result = mysqli_query($conn, $sql);

if (mysqli_num_rows($result) > 0) {
    // output data of each row
    while($row = mysqli_fetch_assoc($result)) {
    echo "id: " . $row["id"]. " - Name: " . $row["firstname"]. "
     " . $row["lastname"]. "
    ";
    }
} else {
    echo "0 results";
}

mysqli_close($conn);
?>

    Example (PDO)

    ` 
    •       
                         
<?php
echo "<table style='border: solid 1px black;'>";
echo "<tr><th>Id</th><th>Firstname
</th><th>Lastname</th></tr>";

class TableRows extends RecursiveIteratorIterator {
    function __construct($it) {
    parent::__construct($it, self::LEAVES_ONLY);
    }

    function current() {
    return "<td style='width:150px;border:1px solid black;'>" 
    . parent::current(). "</td>";
    }

    function beginChildren() {
    echo "<tr>";
    }

    function endChildren() {
    echo "</tr>" . "\n";
    }
}

$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDBPDO";

try {
    $conn = new PDO("mysql:host=$servername;dbname=$dbname", 
    $username, $password);
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO:
    :ERRMODE_EXCEPTION);
    $stmt = $conn->prepare("SELECT id, firstname, lastname 
    FROM MyGuests WHERE lastname='Doe'");
    $stmt->execute();

    // set the resulting array to associative
    $result = $stmt->setFetchMode(PDO::FETCH_ASSOC);
    foreach(new TableRows(new RecursiveArrayIterator($stmt-
    >fetchAll())) as $k=>$v) {
    echo $v;
    }
}
catch(PDOException $e) {
    echo "Error: " . $e->getMessage();
}
$conn = null;
echo "</table>";
?<

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