The ORDER BY clause is used with the SELECT statement to retrieve data from a table sorted by a specific field. It allows you to specify the field name to sort by and the sort direction, either ascending (ASC) or descending (DESC).
The basic syntax of the ORDER BY clause is:
Let's create a SQL query using the ORDER BY clause in a SELECT statement. We will then execute this query by passing it to the PHP mysqli_query() function to retrieve the sorted data. Consider the following persons table inside the demo database:
+----+------------+-----------+----------------------+ | id | first_name | last_name | email | +----+------------+-----------+----------------------+ | 1 | Peter | Parker | peterparker@mail.com | | 2 | John | Rambo | johnrambo@mail.com | | 3 | Clark | Kent | clarkkent@mail.com | | 4 | John | Carter | johncarter@mail.com | | 5 | Harry | Potter | harrypotter@mail.com | +----+------------+-----------+----------------------+
The PHP code below retrieves all records from the persons table and sorts them based on the first_name column in ascending alphabetical order.
<?php
/* Attempt MySQL server connection. Assuming you are running MySQL
server with default setting (user 'root' with no password) */
$link = mysqli_connect("localhost", "root", "", "demo");
// Check connection
if($link === false){
die("ERROR: Could not connect. " . mysqli_connect_error());
}
// Attempt select query execution with order by clause
$sql = "SELECT * FROM persons ORDER BY first_name";
if($result = mysqli_query($link, $sql)){
if(mysqli_num_rows($result) > 0){
echo "<table>";
echo "<tr>";
echo "<th>id</th>";
echo "<th>first_name</th>";
echo "<th>last_name</th>";
echo "<th>email</th>";
echo "</tr>";
while($row = mysqli_fetch_array($result)){
echo "<tr>";
echo "<td>" . $row['id'] . "</td>";
echo "<td>" . $row['first_name'] . "</td>";
echo "<td>" . $row['last_name'] . "</td>";
echo "<td>" . $row['email'] . "</td>";
echo "</tr>";
}
echo "</table>";
// Close result set
mysqli_free_result($result);
} else{
echo "No records matching your query were found.";
}
} else{
echo "ERROR: Could not able to execute $sql. " . mysqli_error($link);
}
// Close connection
mysqli_close($link);
?>
After ordering the results, the dataset will appear as follows:
+----+------------+-----------+----------------------+ | id | first_name | last_name | email | +----+------------+-----------+----------------------+ | 3 | Clark | Kent | clarkkent@mail.com | | 5 | Harry | Potter | harrypotter@mail.com | | 2 | John | Rambo | johnrambo@mail.com | | 4 | John | Carter | johncarter@mail.com | | 1 | Peter | Parker | peterparker@mail.com | +----+------------+-----------+----------------------+
Tip: By default, the ORDER BY clause sorts results in ascending order. To sort records in descending order, use the DESC keyword.