I update a field after a very banal query (call it the WANTED update).

After that, this crazy thing happens: if I load a page of statistics
(=selects) to see the newly updated values after the mentioned update query
has run, it results updates by 3 numbers rather than increased just by 1.
I am absolutely, positively sure the WANTED update increased only by 1: I
printed the result all in the page, No weird addition ensued. But uponm
issuing a select, the value gets updated... again, even 3 times
occasionally.

If I reload again the statistics (that is, I deliver one more select), it
doesn't happen.

Morale, an update, followed by a select, updates (this is not wanted!) the
selected fields of more than 2 or 3 digits. If another select follows on the
same table, no unwanted updates occurs.

Anyone ever met such bad issue before?

DETAILS IF NEEDED FOLLOW:
------------------------------

"SELECT RXamount FROM RXtable WHERE RXcat LIKE 'urban' AND
RXid={$_GET['city']} LIMIT 1"

If that statement returns no result, Insert

"INSERT INTO RXtable VALUES ('urban', {$_GET['city']}, 1)"

otherwise Update:


"UPDATE RXtable SET RXamount=RXamount+1 WHERE RXcat LIKE 'urban' AND
RXid={$_GET['city']} LIMIT 1"

These two statements are correct, I tested them printing the outcome in may
page section, always reporting the right value of either 1 or added 1

Then I go to the page that shwos the statistics:

"SELECT RXid, RXamount FROM RXtable WHERE RXcat LIKE 'urban' ORDER BY
RXamount DESC LIMIT 50" //get city filter not needed here: i want 50
results, not to pinpoint a specific one to update

The first time this last select runs, it shows a value increased by 2 more
digits instead then 1 in the RXamount of the specific RXid record previously
updated (or inserted). If I load the page again, it shows no such behaviour.
If I wait say 5 minutes and I repeat the process, the behaviour repats
itself.
No tables are locked, so the 5 min thing can't be due to locks.

queried table structure quick overview:
ENUM NOT NULL
MEDIUMINT NOT NULL
BIGINT NOT NULL

These queries work as EXPECTED on localhost mysql 5.0.24 but on server Mysql
5.1.11 exhibit the mentioned problem.

I am getting insane after this.

I now performed an update, i printed the result before and after:
before= 2
after= 3
Correct.

I now go on... MySql Administrator and check the stored value, namely
WITHOUT using the website script, I perform a SELECT via MySql
administrator: stored value revealed:
4

Now, I did not alter the data, because I read it via MySql Admin, I just
issued a select. The select has updated again...