huh? select * from table where integer = '1a' ....

Why does a select from table with an integer field return a row if I compare
the integer to an alpha character?

Here's the info ( a straight copy and paste), then compare my two select
statements:

mysql> desc product;
+------------------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+------------------+--------------+------+-----+---------+-------+
| prd_id | int(11) | | PRI | 0 | |
| prd_name | varchar(30) | | | | |
| prd_short_desc | varchar(250) | YES | | NULL | |
| prd_long_desc1 | text | YES | | NULL | |
| prd_long_desc2 | text | YES | | NULL | |
| prd_long_desc3 | text | YES | | NULL | |
| prd_thumb | varchar(250) | YES | | NULL | |
| prd_full_image | varchar(250) | YES | | NULL | |
| prd_price | decimal(8,2) | YES | | NULL | |
| prd_custom1 | varchar(10) | YES | | NULL | |
| prd_custom2 | varchar(10) | YES | | NULL | |
| prd_start_date | date | YES | | NULL | |
| prd_end_date | date | YES | | NULL | |
| prd_instock | int(11) | | | 0 | |
| prd_search_words | text | YES | | NULL | |
+------------------+--------------+------+-----+---------+-------+
15 rows in set (0.00 sec)

mysql> select prd_id from product where prd_id = 33;
+--------+
| prd_id |
+--------+
| 33 |
+--------+
1 row in set (0.01 sec)

mysql> select prd_id from product where prd_id = '33a';
+--------+
| prd_id |
+--------+
| 33 |
+--------+
1 row in set (0.00 sec)

mysql> select version();
+-----------+
| version() |
+-----------+
| 3.23.32 |
+-----------+
1 row in set (0.00 sec)

mysql>


notice that
select prd_id from product where prd_id = 33;
and
select prd_id from product where prd_id = '33a';
both reutrun a row, the same row actually!

I noticed that this returns nothing:
select prd_id from product where prd_id = 'a33';

So 'What Gives?'

I can't seem to track down any info about this so any insight would be
great.
(please notice that my version is 3.23.32)

Thanks in advandce
JohnL