PHP MySQL The WHERE Clause
Select and Filter Data From a MySQL Database
The SQL 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
To learn more about SQL, please visit our SQL tutorial.
Select and Filter Data With MySQLi
The following example selects the id, firstname and lastname columns from the MyGuests table where the lastname is "Doe", and displays it on the page:
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'";
// Execute the SQL query
$result = $conn->query($sql);
// Process
the result set
if ($result->num_rows > 0) {
// Output data of each row
while($row = $result->fetch_assoc()) {
echo "id: " . $row["id"]. " - Name: " . $row["firstname"]. " " . $row["lastname"]. "<br>";
}
} else {
echo "0 results";
}
$conn->close();
?>
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Code Explanation
First, we set up an SQL query that selects the id, firstname and lastname columns from the MyGuests table where the lastname is "Doe".
The next line of code, $conn->query($sql), runs the query and puts the resulting data into a
variable called $result.
Then, the line $result->num_rows>0 checks if there are more than
0
rows returned.
If there are more than 0 rows returned, the
function fetch_assoc() puts the result
set 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.
The following example shows the same as the example above, in the MySQLi procedural way:
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"]. " " . $row["lastname"]. "<br>";
}
} else {
echo "0 results";
}
mysqli_close($conn);
?>
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Put Result in HTML Table
Here, we put the result in an HTML table:
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 ($result->num_rows > 0) {
echo "<table><tr><th>ID</th><th>Name</th></tr>";
// output data of each row
while($row = $result->fetch_assoc()) {
echo "<tr><td>".$row["id"]."</td><td>".$row["firstname"]." ".$row["lastname"]."</td></tr>";
}
echo "</table>";
} else {
echo "0 results";
}
$conn->close();
?>
Run example »
Select and Filter Data With PDO
The following example selects the id, firstname and lastname columns from the MyGuests table where the lastname is "Doe", and displays it in an HTML table:
Example - PDO
<?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";
try {
$conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
// set the PDO error mode to exception
$conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
} catch(PDOException $e){
die("Could not connect. " .
$e->getMessage());
}
try {
$sql = "SELECT id,
firstname, lastname FROM MyGuests WHERE lastname='Doe'";
// Execute the SQL query
$result = $conn->query($sql);
//
Process the result set
if ($result->rowCount() > 0) {
echo
"<table><tr><th>ID</th><th>Firstname</th><th>Lastname</th></tr>";
// Output data of each row
while($row = $result->fetch()) {
echo
"<tr>";
echo "<td>" . $row['id'] . "</td>";
echo "<td>" . $row['firstname'] . "</td>";
echo "<td>" . $row['lastname'] . "</td>";
echo "</tr>";
}
echo "</table>";
unset($result);
else {
echo "No records
found.";
}
} catch(PDOException $e) {
echo "Error: " . $e->getMessage();
}
$conn = null;
?>
