When is a timestamp (auto) updated?

Question

If I have a column in a table of type TIMESTAMP and has as default: CURRENT_TIMESTAMP does this column get updated to the current timestamp if I update the value of any other column in the the same row?
It seems that it does not but I am not sure if this is what should happen.
I can not understand what this means (from MySQL documentation):

If the column is auto-updated, it is automatically updated to the current timestamp when the value of any other column in the row is changed from its current value. The column remains unchanged if all other columns are set to their current values. To prevent the column from updating when other columns change, explicitly set it to its current value. To update the column even when other columns do not change, explicitly set it to the value it should have]2

Answer 1

Give the command SHOW CREATE TABLE whatever

Then look at the table definition.

It probably has a line like this

logtime TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP, 

in it. DEFAULT CURRENT_TIMESTAMP means that any INSERT without an explicit time stamp setting uses the current time. Likewise, ON UPDATE CURRENT_TIMESTAMP means that any update without an explicit timestamp results in an update to the current timestamp value.

You can control this default behavior when creating your table.

Or, if the timestamp column wasn't created correctly in the first place, you can change it.

ALTER TABLE whatevertable      CHANGE whatevercolumn              whatevercolumn TIMESTAMP NOT NULL                            DEFAULT CURRENT_TIMESTAMP                             ON UPDATE CURRENT_TIMESTAMP; 

This will cause both INSERT and UPDATE operations on the table automatically to update your timestamp column. If you want to update whatevertable without changing the timestamp, that is,

To prevent the column from updating when other columns change

then you need to issue this kind of update.

UPDATE whatevertable    SET something = 'newvalue',        whatevercolumn = whatevercolumn  WHERE someindex = 'indexvalue' 

This works with TIMESTAMP and DATETIME columns. (Prior to MySQL version 5.6.5 it only worked with TIMESTAMPs) When you use TIMESTAMPs, time zones are accounted for: on a correctly configured server machine, those values are always stored in UTC and translated to local time upon retrieval.

Answer 2

I think you have to define the timestamp column like this

 CREATE TABLE t1  (     ts TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP ); 

See here