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?
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'];
}
?>
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.
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.
The simplest thing would be to check the timestamp of the table files on the disk. For example, You can check under your data directory
cd /var/lib/mysql/<mydatabase>
ls -lhtr *.ibd
This should give you the list of all tables with the table when it was last modified the oldest time, first.
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.
For a list of recent table changes use this:
SELECT UPDATE_TIME, TABLE_SCHEMA, TABLE_NAME
FROM information_schema.tables
ORDER BY UPDATE_TIME DESC, TABLE_SCHEMA, TABLE_NAME
i made a column by name : update-at in phpMyAdmin and got the current time from Date() method in my code (nodejs) . with every change in table this column hold the time of changes.
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.
For a list of recent table changes use this:
SELECT UPDATE_TIME, TABLE_SCHEMA, TABLE_NAME
FROM information_schema.tables
ORDER BY UPDATE_TIME DESC, TABLE_SCHEMA, TABLE_NAME
I'm surprised no one has suggested tracking last update time per row:
mysql> CREATE TABLE foo (
id INT PRIMARY KEY
x INT,
updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
ON UPDATE CURRENT_TIMESTAMP,
KEY (updated_at)
);
mysql> INSERT INTO foo VALUES (1, NOW() - INTERVAL 3 DAY), (2, NOW());
mysql> SELECT * FROM foo;
+----+------+---------------------+
| id | x | updated_at |
+----+------+---------------------+
| 1 | NULL | 2013-08-18 03:26:28 |
| 2 | NULL | 2013-08-21 03:26:28 |
+----+------+---------------------+
mysql> UPDATE foo SET x = 1234 WHERE id = 1;
This updates the timestamp even though we didn't mention it in the UPDATE.
mysql> SELECT * FROM foo;
+----+------+---------------------+
| id | x | updated_at |
+----+------+---------------------+
| 1 | 1235 | 2013-08-21 03:30:20 | <-- this row has been updated
| 2 | NULL | 2013-08-21 03:26:28 |
+----+------+---------------------+
Now you can query for the MAX():
mysql> SELECT MAX(updated_at) FROM foo;
+---------------------+
| MAX(updated_at) |
+---------------------+
| 2013-08-21 03:30:20 |
+---------------------+
Admittedly, this requires more storage (4 bytes per row for TIMESTAMP).
But this works for InnoDB tables before 5.7.15 version of MySQL, which INFORMATION_SCHEMA.TABLES.UPDATE_TIME doesn't.
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
I got this to work locally, but not on my shared host for my public website (rights issue I think).
SELECT last_update FROM mysql.innodb_table_stats WHERE table_name = 'yourTblName';
'2020-10-09 08:25:10'
MySQL 5.7.20-log on Win 8.1
I don't have information_schema database, using mysql version 4.1.16, so in this case you can query this:
SHOW TABLE STATUS FROM your_database LIKE 'your_table';
It will return these columns:
| Name | Engine | Version | Row_format | Rows | Avg_row_length
| Data_length | Max_data_length | Index_length | Data_free | Auto_increment
| Create_time | Update_time | Check_time | Collation
| Checksum | Create_options | Comment |
As you can see there is a column called: "Update_time" that shows you the last update time for your_table.
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.
a) It will show you all tables and there last update dates
SHOW TABLE STATUS FROM db_name;
then, you can further ask for specific table:
SHOW TABLE STATUS FROM db_name like 'table_name';
b) As in above examples you cannot use sorting on 'Update_time' but using SELECT you can:
SELECT * FROM information_schema.tables WHERE TABLE_SCHEMA='db_name' ORDER BY UPDATE_TIME DESC;
to further ask about particular table:
SELECT * FROM information_schema.tables WHERE TABLE_SCHEMA='db_name' AND table_name='table_name' ORDER BY UPDATE_TIME DESC';
The simplest thing would be to check the timestamp of the table files on the disk. For example, You can check under your data directory
cd /var/lib/mysql/<mydatabase>
ls -lhtr *.ibd
This should give you the list of all tables with the table when it was last modified the oldest time, first.
Although there is an accepted answer I don't feel that it is the right one. It is the simplest way to achieve what is needed, but even if already enabled in InnoDB (actually docs tell you that you still should get NULL ...), if you read MySQL docs, even in current version (8.0) using UPDATE_TIME is not the right option, because:
Timestamps are not persisted when the server is restarted or when the table is evicted from the InnoDB data dictionary cache.
If I understand correctly (can't verify it on a server right now), timestamp gets reset after server restart.
As for real (and, well, costly) solutions, you have Bill Karwin's solution with CURRENT_TIMESTAMP and I'd like to propose a different one, that is based on triggers (I'm using that one).
You start by creating a separate table (or maybe you have some other table that can be used for this purpose) which will work like a storage for global variables (here timestamps). You need to store two fields - table name (or whatever value you'd like to keep here as table id) and timestamp. After you have it, you should initialize it with this table id + starting date (NOW() is a good choice :) ).
Now, you move to tables you want to observe and add triggers AFTER INSERT/UPDATE/DELETE with this or similar procedure:
CREATE PROCEDURE `timestamp_update` ()
BEGIN
UPDATE `SCHEMA_NAME`.`TIMESTAMPS_TABLE_NAME`
SET `timestamp_column`=DATE_FORMAT(NOW(), '%Y-%m-%d %T')
WHERE `table_name_column`='TABLE_NAME';
END
I would create a trigger that catches all updates/inserts/deletes and write timestamp in custom table, something like tablename | timestamp
Just because I don't like the idea to read internal system tables of db server directly
OS level analysis:
Find where the DB is stored on disk:
grep datadir /etc/my.cnf
datadir=/var/lib/mysql
Check for most recent modifications
cd /var/lib/mysql/{db_name}
ls -lrt
Should work on all database types.
i made a column by name : update-at in phpMyAdmin and got the current time from Date() method in my code (nodejs) . with every change in table this column hold the time of changes.
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.
I'm surprised no one has suggested tracking last update time per row:
mysql> CREATE TABLE foo (
id INT PRIMARY KEY
x INT,
updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
ON UPDATE CURRENT_TIMESTAMP,
KEY (updated_at)
);
mysql> INSERT INTO foo VALUES (1, NOW() - INTERVAL 3 DAY), (2, NOW());
mysql> SELECT * FROM foo;
+----+------+---------------------+
| id | x | updated_at |
+----+------+---------------------+
| 1 | NULL | 2013-08-18 03:26:28 |
| 2 | NULL | 2013-08-21 03:26:28 |
+----+------+---------------------+
mysql> UPDATE foo SET x = 1234 WHERE id = 1;
This updates the timestamp even though we didn't mention it in the UPDATE.
mysql> SELECT * FROM foo;
+----+------+---------------------+
| id | x | updated_at |
+----+------+---------------------+
| 1 | 1235 | 2013-08-21 03:30:20 | <-- this row has been updated
| 2 | NULL | 2013-08-21 03:26:28 |
+----+------+---------------------+
Now you can query for the MAX():
mysql> SELECT MAX(updated_at) FROM foo;
+---------------------+
| MAX(updated_at) |
+---------------------+
| 2013-08-21 03:30:20 |
+---------------------+
Admittedly, this requires more storage (4 bytes per row for TIMESTAMP).
But this works for InnoDB tables before 5.7.15 version of MySQL, which INFORMATION_SCHEMA.TABLES.UPDATE_TIME doesn't.
I would create a trigger that catches all updates/inserts/deletes and write timestamp in custom table, something like tablename | timestamp
Just because I don't like the idea to read internal system tables of db server directly
OS level analysis:
Find where the DB is stored on disk:
grep datadir /etc/my.cnf
datadir=/var/lib/mysql
Check for most recent modifications
cd /var/lib/mysql/{db_name}
ls -lrt
Should work on all database types.
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
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.
I don't have information_schema database, using mysql version 4.1.16, so in this case you can query this:
SHOW TABLE STATUS FROM your_database LIKE 'your_table';
It will return these columns:
| Name | Engine | Version | Row_format | Rows | Avg_row_length
| Data_length | Max_data_length | Index_length | Data_free | Auto_increment
| Create_time | Update_time | Check_time | Collation
| Checksum | Create_options | Comment |
As you can see there is a column called: "Update_time" that shows you the last update time for your_table.
a) It will show you all tables and there last update dates
SHOW TABLE STATUS FROM db_name;
then, you can further ask for specific table:
SHOW TABLE STATUS FROM db_name like 'table_name';
b) As in above examples you cannot use sorting on 'Update_time' but using SELECT you can:
SELECT * FROM information_schema.tables WHERE TABLE_SCHEMA='db_name' ORDER BY UPDATE_TIME DESC;
to further ask about particular table:
SELECT * FROM information_schema.tables WHERE TABLE_SCHEMA='db_name' AND table_name='table_name' ORDER BY UPDATE_TIME DESC';
I got this to work locally, but not on my shared host for my public website (rights issue I think).
SELECT last_update FROM mysql.innodb_table_stats WHERE table_name = 'yourTblName';
'2020-10-09 08:25:10'
MySQL 5.7.20-log on Win 8.1
Although there is an accepted answer I don't feel that it is the right one. It is the simplest way to achieve what is needed, but even if already enabled in InnoDB (actually docs tell you that you still should get NULL ...), if you read MySQL docs, even in current version (8.0) using UPDATE_TIME is not the right option, because:
Timestamps are not persisted when the server is restarted or when the table is evicted from the InnoDB data dictionary cache.
If I understand correctly (can't verify it on a server right now), timestamp gets reset after server restart.
As for real (and, well, costly) solutions, you have Bill Karwin's solution with CURRENT_TIMESTAMP and I'd like to propose a different one, that is based on triggers (I'm using that one).
You start by creating a separate table (or maybe you have some other table that can be used for this purpose) which will work like a storage for global variables (here timestamps). You need to store two fields - table name (or whatever value you'd like to keep here as table id) and timestamp. After you have it, you should initialize it with this table id + starting date (NOW() is a good choice :) ).
Now, you move to tables you want to observe and add triggers AFTER INSERT/UPDATE/DELETE with this or similar procedure:
CREATE PROCEDURE `timestamp_update` ()
BEGIN
UPDATE `SCHEMA_NAME`.`TIMESTAMPS_TABLE_NAME`
SET `timestamp_column`=DATE_FORMAT(NOW(), '%Y-%m-%d %T')
WHERE `table_name_column`='TABLE_NAME';
END
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'];
}
?>
Source: Stackoverflow.com