Question

I have a MySQL table which hen created automatically puts a ISO 8601 timestamp into one of the fields. It does this because I have set the default value thought phpMyAdmin to TIMESTAMP.

When I update the field I want to add another timestamp to another field. Obviously I cant do that using the default option. Is there an SQL command to add a current timestamp to a field? I have had a quick read through the MySQL website but I couldnt find a way to do it…

I also had a look to see if there was a way of generating an ISO8601 timestamp through PHP but I couldnt figure out a way to convert from a PHP/unix timestamp to ISO8601.

Cheers!

Answer 1

MySQL can automatically initialise and/or update a single TIMESTAMP type column within every table to the current time on INSERT and UPDATE. As explained in Automatic Initialization and Updating for TIMESTAMP:

One TIMESTAMP column in a table can have the current timestamp as the default value for initializing the column, as the auto-update value, or both. It is not possible to have the current timestamp be the default value for one column and the auto-update value for another column.

In your case, because you want separate columns to hold the record’s initialisation and update times, you will need to set one (or both) of those columns explicitly; one can explicitly set a date/time column to the current date/time in SQL using the NOW() function:

INSERT INTO my_table (created) VALUES (NOW());
UPDATE my_table SET updated = NOW();

One can even use triggers to achieve the automatic behaviour that is not natively provided by MySQL:

CREATE TRIGGER set_init_time AFTER INSERT ON my_table FOR EACH ROW
  SET NEW.created = NOW();

CREATE TRIGGER set_updt_time AFTER UPDATE ON my_table FOR EACH ROW
  SET NEW.updated = NOW();