Page 422 - Beginning PHP 5.3

Part III: Using PHP in Practice
By using the null - safe operator < = > , you ensure that any NULL value isn ’ t propagated through to the

result:
mysql > select 1 < = > 2;
+---------+
| 1 < = > 2 |
+---------+
| 0 |
+---------+
1 row in set (0.00 sec)

mysql > select 1 < = > NULL;
+------------+
| 1 < = > NULL |
+------------+
| 0 |
+------------+
1 row in set (0.00 sec)

mysql > select NULL < = > NULL;
+---------------+
| NULL < = > NULL |
+---------------+
| 1 |
+---------------+

1 row in set (0.00 sec)
You can also use the Boolean operators AND , OR , and NOT to build more complex expressions. For
example:

mysql > SELECT * FROM accessLog WHERE lastAccess > ‘2008-11-04’ AND lastAccess
< ‘2008-11-09’;
+----------+-------------+-----------+---------------------+
| memberId | pageUrl | numVisits | lastAccess |
+----------+-------------+-----------+---------------------+
| 3 | books.php | 2 | 2008-11-08 19:47:34 |
| 3 | contact.php | 1 | 2008-11-08 14:52:12 |
+----------+-------------+-----------+---------------------+

MySQL ’ s functions can be broken down into many categories. For example, there are many date and
time functions, such as now() , that retrieves the current date and time (useful when comparing dates
and times against the current moment). You can also use curdate() to retrieve just the date portion of
now() , and curtime() to get just the time portion:

mysql > SELECT now(), curdate(), curtime();
+---------------------+------------+-----------+
| now() | curdate() | curtime() |
+---------------------+------------+-----------+
| 2008-11-09 12:17:08 | 2008-11-09 | 12:17:08 |
+---------------------+------------+-----------+

1 row in set (0.08 sec)

384

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