We have seen the SQL SELECT command along with the WHERE clause to fetch data from a MySQL table, but when we try to give a condition, which compares the field or the column value to NULL, it does not work properly.
To handle such a situation, MySQL provides three operators −
IS NULL − This operator returns true, if the column value is NULL.
IS NOT NULL − This operator returns true, if the column value is not NULL.
<=> − This operator compares values, which (unlike the = operator) is true even for two NULL values.
The conditions involving NULL are special. You cannot use = NULL or != NULL to look for NULL values in columns. Such comparisons always fail because it is impossible to tell whether they are true or not. Sometimes, even NULL = NULL fails.
To look for columns that are or are not NULL, use IS NULL or IS NOT NULL.
You can use the if...else condition to prepare a query based on the NULL value.
The following example takes the tutorial_count from outside and then compares it with the value available in the table.
<?php $dbhost = 'remotemysql.com:3036'; $dbuser = 'your_username; $dbpass = 'your_password'; $conn = mysqli_connect($dbhost, $dbuser, $dbpass); if(! $conn ) { die('Could not connect: ' . mysqli_error()); } if( isset($tutorial_count )) { $sql = 'SELECT tutorial_author, tutorial_count FROM tcount_tbl WHERE tutorial_count = $tutorial_count'; } else { $sql = 'SELECT tutorial_author, tutorial_count FROM tcount_tbl WHERE tutorial_count IS $tutorial_count'; } mysqli_select_db('TUTORIALS'); $retval = mysqli_query( $sql, $conn ); if(! $retval ) { die('Could not get data: ' . mysqli_error()); } while($row = mysqli_fetch_array($retval, mysqli_ASSOC)) { echo "Author:{$row['tutorial_author']} <br> ". "Count: {$row['tutorial_count']} <br> ". "--------------------------------<br>"; } echo "Fetched data successfully\n"; mysqli_close($conn); ?>