How can I tell when a MySQL table was last updated

Question

In the footer of my page, I would like to add something like "last updated the xx/xx/200x" with this date being the last time a certain mySQL table has been updated.

What is the best way to do that? Is there a function to retrieve the last updated date? Should I access to the database every time I need this value?

Answer 1

Just grab the file date modified from file system. In my language that is:

 tbl_updated = file.update_time(
        "C:\ProgramData\MySQL\MySQL Server 5.5\data\mydb\person.frm")

Output:

1/25/2013 06:04:10 AM

Answer 2

In later versions of MySQL you can use the information_schema database to tell you when another table was updated:

SELECT UPDATE_TIME
FROM   information_schema.tables
WHERE  TABLE_SCHEMA = 'dbname'
   AND TABLE_NAME = 'tabname'

This does of course mean opening a connection to the database.

---

An alternative option would be to "touch" a particular file whenever the MySQL table is updated:

On database updates:

• Open your timestamp file in O_RDRW mode
• close it again

or alternatively

• use touch(), the PHP equivalent of the utimes() function, to change the file timestamp.

On page display:

• use stat() to read back the file modification time.

Answer 3

Not sure if this would be of any interest. Using mysqlproxy in between mysql and clients, and making use of a lua script to update a key value in memcached according to interesting table changes UPDATE,DELETE,INSERT was the solution which I did quite recently. If the wrapper supported hooks or triggers in php, this could have been eaiser. None of the wrappers as of now does this.

Answer 4

This is what I did, I hope it helps.

<?php
    mysql_connect("localhost", "USER", "PASSWORD") or die(mysql_error());
    mysql_select_db("information_schema") or die(mysql_error());
    $query1 = "SELECT `UPDATE_TIME` FROM `TABLES` WHERE
        `TABLE_SCHEMA` LIKE 'DataBaseName' AND `TABLE_NAME` LIKE 'TableName'";
    $result1 = mysql_query($query1) or die(mysql_error());
    while($row = mysql_fetch_array($result1)) {
        echo "<strong>1r tr.: </strong>".$row['UPDATE_TIME'];
    }
?>

Answer 5

If you are running Linux you can use inotify to look at the table or the database directory. inotify is available from PHP, node.js, perl and I suspect most other languages. Of course you must have installed inotify or had your ISP install it. A lot of ISP will not.

Answer 6

Cache the query in a global variable when it is not available.

Create a webpage to force the cache to be reloaded when you update it.

Add a call to the reloading page into your deployment scripts.