PHP MySQL WHERE Clause

 

Filtering the Records

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

The basic syntax of the WHERE clause can be given with:

SELECT column_name(s) FROM table_name WHERE column_name operator value

Let's make a SQL query using the WHERE clause in SELECT statement, after that we'll execute this query through passing it to the PHP mysqli_query() function to get the filtered data.

Consider we've a persons table inside the demo database that has following records:

+----+------------+-----------+----------------------+
| id | first_name | last_name | email                |
+----+------------+-----------+----------------------+
|  1 | Peter      | Parker    | [email protected] |
|  2 | John       | Rambo     | [email protected]   |
|  3 | Clark      | Kent      | [email protected]   |
|  4 | John       | Carter    | [email protected]  |
|  5 | Harry      | Potter    | [email protected] |
+----+------------+-----------+----------------------+

The following PHP code selects all the rows from the persons table where first_name='john':

Code

<?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 $sql = "SELECT * FROM persons WHERE first_name='john'"; if($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 filtration the result set will look something like this:

+----+------------+-----------+---------------------+
| id | first_name | last_name | email               |
+----+------------+-----------+---------------------+
|  2 | John       | Rambo     | [email protected]  |
|  4 | John       | Carter    | [email protected] |
+----+------------+-----------+---------------------+