type - mysql timestamp example




Should I use the datetime or timestamp data type in MySQL? (20)

Would you recommend using a datetime or a timestamp field, and why (using MySQL)?

I'm working with PHP on the server side.


2016 +: what I advise is to set your Mysql timezone to UTC and use DATETIME:

Any recent front-end framework (Angular 1/2, react, Vue,...) can easily and automatically convert your UTC datetime to local time.

Additionally:

(Unless you are likely to change the timezone of your servers)


Example with AngularJs

// back-end: format for angular within the sql query
SELECT DATE_FORMAT(my_datetime, "%Y-%m-%dT%TZ")...

// font-end Output the localised time
{{item.my_datetime | date :'medium' }}

All localised time format available here: https://docs.angularjs.org/api/ng/filter/date


  1. TIMESTAMP is four bytes vs eight bytes for DATETIME.

  2. Timestamps are also lighter on the database and indexed faster.

  3. The DATETIME type is used when you need values that contain both date and time information. MySQL retrieves and displays DATETIME values in ‘YYYY-MM-DD HH:MM:SS’ format. The supported range is ’1000-01-01 00:00:00′ to ’9999-12-31 23:59:59′.

The TIMESTAMP data type has a range of ’1970-01-01 00:00:01′ UTC to ’2038-01-09 03:14:07′ UTC. It has varying properties, depending on the MySQL version and the SQL mode the server is running in.

  1. DATETIME is constant while TIMESTAMP is effected by the time_zone setting.

A TIMESTAMP requires 4 bytes, whereas a DATETIME requires 8 bytes.


A timestamp field is a special case of the datetime field. You can create timestamp columns to have special properties; it can be set to update itself on either create and/or update.

In "bigger" database terms, timestamp has a couple of special-case triggers on it.

What the right one is depends entirely on what you want to do.


Beware of timestamp changing when you do a UPDATE statement on a table. If you have a table with columns 'Name' (varchar), 'Age' (int), and 'Date_Added' (timestamp) and you run the following DML statement

UPDATE table
SET age = 30

then every single value in your 'Date_Added' column would be changed to the current timestamp.


Comparison between DATETIME, TIMESTAMP and DATE

What is that [.fraction]?

  • A DATETIME or TIMESTAMP value can include a trailing fractional seconds part in up to microseconds (6 digits) precision. In particular, any fractional part in a value inserted into a DATETIME or TIMESTAMP column is stored rather than discarded. This is of course optional.

Sources:


From my experiences, if you want a date field in which insertion happens only once and you don't want to have any update or any other action on that particular field, go with date time.

For example, consider a user table with a REGISTRATION DATE field. In that user table, if you want to know the last logged in time of a particular user, go with a field of timestamp type so that the field gets updated.

If you are creating the table from phpMyAdmin the default setting will update the timestamp field when a row update happens. If your timestamp filed is not updating with row update, you can use the following query to make a timestamp field get auto updated.

ALTER TABLE your_table
      MODIFY COLUMN ts_activity TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP;

I always use DATETIME fields for anything other than row metadata (date created or modified).

As mentioned in the MySQL documentation:

The DATETIME type is used when you need values that contain both date and time information. MySQL retrieves and displays DATETIME values in 'YYYY-MM-DD HH:MM:SS' format. The supported range is '1000-01-01 00:00:00' to '9999-12-31 23:59:59'.

...

The TIMESTAMP data type has a range of '1970-01-01 00:00:01' UTC to '2038-01-09 03:14:07' UTC. It has varying properties, depending on the MySQL version and the SQL mode the server is running in.

You're quite likely to hit the lower limit on TIMESTAMPs in general use -- e.g. storing birthdate.


I found unsurpassed usefulness in TIMESTAMP's ability to auto update itself based on the current time without the use of unnecessary triggers. That's just me though, although TIMESTAMP is UTC like it was said.

It can keep track across different timezones, so if you need to display a relative time for instance, UTC time is what you would want.


I like a Unix timestamp, because you can convert to numbers and just worry about the number. Plus you add/subtract and get durations, etc. Then convert the result to Date in whatever format. This code finds out how much time in minutes passed between a timestamp from a document, and the current time.

$date  = $item['pubdate']; (etc ...)
$unix_now = time();
$result = strtotime($date, $unix_now);
$unix_diff_min = (($unix_now  - $result) / 60);
$min = round($unix_diff_min);

I merely use unsigned BIGINT while storing UTC ...

which then still can be adjusted to local time in PHP.

the DATETIME to be selected with FROM_UNIXTIME( integer_timestamp_column ).

one obviously should set an index on that column, else there would be no advance.


I prefer using timestamp so to keep everything in one common raw format and format the data in PHP code or in your SQL query. There are instances where it comes in handy in your code to keep everything in plain seconds.


I would always use a Unix timestamp when working with MySQL and PHP. The main reason for this being the the default date method in PHP uses a timestamp as the parameter, so there would be no parsing needed.

To get the current Unix timestamp in PHP, just do time();
and in MySQL do SELECT UNIX_TIMESTAMP();.


In MySQL 5 and above, TIMESTAMP values are converted from the current time zone to UTC for storage, and converted back from UTC to the current time zone for retrieval. (This occurs only for the TIMESTAMP data type, and not for other types such as DATETIME.)

By default, the current time zone for each connection is the server's time. The time zone can be set on a per-connection basis, as described in MySQL Server Time Zone Support.


It is worth noting in MySQL you can use something along the lines of the below when creating your table columns:

on update CURRENT_TIMESTAMP

This will update the time at each instance you modify a row and is sometimes very helpful for stored last edit information. This only works with timestamp, not datetime however.



TIMESTAMP is useful when you have visitors from different countries with different time zones. you can easily convert the TIMESTAMP to any country time zone


The below examples show how the TIMESTAMP date type changed the values after changing the time-zone to 'america/new_york' where DATETIMEis unchanged.

mysql> show variables like '%time_zone%';
+------------------+---------------------+
| Variable_name    | Value               |
+------------------+---------------------+
| system_time_zone | India Standard Time |
| time_zone        | Asia/Calcutta       |
+------------------+---------------------+

mysql> create table datedemo(
    -> mydatetime datetime,
    -> mytimestamp timestamp
    -> );

mysql> insert into datedemo values ((now()),(now()));

mysql> select * from datedemo;
+---------------------+---------------------+
| mydatetime          | mytimestamp         |
+---------------------+---------------------+
| 2011-08-21 14:11:09 | 2011-08-21 14:11:09 |
+---------------------+---------------------+

mysql> set time_zone="america/new_york";

mysql> select * from datedemo;
+---------------------+---------------------+
| mydatetime          | mytimestamp         |
+---------------------+---------------------+
| 2011-08-21 14:11:09 | 2011-08-21 04:41:09 |
+---------------------+---------------------+

I've converted my answer into article so more people can find this useful, MySQL: Datetime Versus Timestamp Data Types.



The timestamp data type stores date and time, but in UTC format, not in the current timezone format as datetime does. And when you fetch data, timestamp again converts that into the current timezone time.

So suppose you are in USA and getting data from a server which has a time zone of USA. Then you will get the date and time according to the USA time zone. The timestamp data type column always get updated automatically when its row gets updated. So it can be useful to track when a particular row was updated last time.

For more details you can read the blog post Timestamp Vs Datetime .







sqldatatypes