I am trying to convert long date format string (e.g. 1st-June-1999 or 20th-March-2001) to date YYYY-MM-DD using MySql 5.7.
Reading docs tried to use STR_TO_DATE:
select STR_TO_DATE(dob,'%d-%M-YYYY') from table
However, this returns null due to the day suffix (e.g. th).
I could use update query with REPLACE() to remove the suffix and then STR_TO_DATE, but is there a better solution?
You have two problems. First, you need %D (capital not lowercase) since you have the suffix after the day of the month.
Next, the year should simply be %Y.
So, the select statement would be
select STR_TO_DATE(dob,'%D-%M-%Y') from table;
w3schools has a good reference for the abbreviations: https://www.w3schools.com/sql/func_mysql_str_to_date.asp
%D does what you want:
str_to_date(dob, '%D-%M-%Y')
A couple of questions.
In SQL Developer I could type alter session set nls_date_format='DD-MON-YY HH:24:MI:SS'; to include the time and all queries on that tab would then include this format. I could then type alter session set nls_date_format='DD-MON-YY'; to remove the time. Any easy equivalent in MySQL that could flip my date formats like this?
If it's not that simple, let me ask this: Can the format be changed on a single query line. So if i have this
select name, start_date from Users;
If this normally shows the date and time, how can i alter it to only have the results show just the date?
Any easy equivalent in MySQL that could flip my date formats like this?
Yes, there is.
What you're looking for is the DATE_FORMAT() function.
Example:
select DATE_FORMAT(start_date,'%d-%m-%Y') from Users
Adjust the specifiers as needed.
Common specifiers:
%d day of month
%m month
%Y year
%H hour (00..23)
%h hour (01..12)
%p AM or PM
%i minutes
%s seconds
For other specifiers, see DATE_FORMAT().
start_date is presumably a datetime column. You can truncate the time by converting it to a date:
SELECT name, DATE(start_date)
FROM users
How to convert a timestamp into custom formated string with timezone in MySQL?
This is how I am selecting the timestamp right now. Its correctly formated, but lacks timezone. updated is the name of the timestamp field.
SELECT DATE_FORMAT(updated, '%e.%c.%Y %T') AS updated FROM table;
returns strings like this:
29.1.2015 12:43:16
Then I tried adding timezone like this, but I am getting NULLs as return values.
SELECT DATE_FORMAT(CONVERT_TZ(updated, 'GMT', 'Europe/Helsinki'), '%e.%c.%Y %T') AS updated FROM table;
i use 1383123123 instead timestamp field
Select FROM_UNIXTIME(1383123123);
the result is '2013-10-30 10:52:03'
Select CONVERT_TZ(FROM_UNIXTIME(1383123123), '+00:00', '+02:00')
the result is '2013-10-30 12:52:03'
'Europe/Helsinki' time zone means "gmt+2"
Follow up question of
https://serverfault.com/questions/191331/should-servers-have-their-timezone-set-to-gmt-utc
Should the MySQL timezone be set to UTC or should it be set to be the same timezone as the server or PHP is set? (If it is not UTC)
What are the pros and cons?
It seems that it does not matter what timezone is on the server as long as you have the time set right for the current timezone, know the timezone of the datetime columns that you store, and are aware of the issues with daylight savings time.
On the other hand if you have control of the timezones of the servers you work with then you can have everything set to UTC internally and never worry about timezones and DST, at least when it comes to storing internal time.
Here are some notes I collected of how to work with timezones as a form of cheatsheet for myself and others which might influence what timezone the person will choose for his/her server and how he/she will store date and time.
MySQL Timezone Cheatsheet
Notes:
Changing the timezone will not change the stored datetime or
timestamp, but it will select a different datetime from
timestamp columns
Warning! UTC has leap seconds, these look like '2012-06-30 23:59:60' and can
be added randomly, with 6 months prior notice, due to the slowing of
the earths rotation
GMT confuses seconds, which is why UTC was invented.
Warning! different regional timezones might produce the same datetime value due
to daylight savings time
The timestamp column only supports dates 1970-01-01 00:00:01 to 2038-01-19 03:14:07 UTC, due to a limitation.
Internally a MySQL timestamp column is stored as UTC but
when selecting a date MySQL will automatically convert it to the
current session timezone.
When storing a date in a timestamp, MySQL will assume that the date
is in the current session timezone and convert it to UTC for
storage.
MySQL can store partial dates in datetime columns, these look like
"2013-00-00 04:00:00"
MySQL stores "0000-00-00 00:00:00" if you set a datetime column as
NULL, unless you specifically set the column to allow null when you
create it.
Read this
To select a timestamp column in UTC format
no matter what timezone the current MySQL session is in:
SELECT
CONVERT_TZ(`timestamp_field`, ##session.time_zone, '+00:00') AS `utc_datetime`
FROM `table_name`
You can also set the sever or global or current session timezone to UTC and then select the timestamp like so:
SELECT `timestamp_field` FROM `table_name`
To select the current datetime in UTC:
SELECT UTC_TIMESTAMP();
SELECT UTC_TIMESTAMP;
SELECT CONVERT_TZ(NOW(), ##session.time_zone, '+00:00');
Example result: 2015-03-24 17:02:41
To select the current datetime in the session timezone
SELECT NOW();
SELECT CURRENT_TIMESTAMP;
SELECT CURRENT_TIMESTAMP();
To select the timezone that was set when the server launched
SELECT ##system_time_zone;
Returns "MSK" or "+04:00" for Moscow time for example, there is (or was) a MySQL bug where if set to a numerical offset it would not adjust the Daylight savings time
To get the current timezone
SELECT TIMEDIFF(NOW(), UTC_TIMESTAMP);
It will return 02:00:00 if your timezone is +2:00.
To get the current UNIX timestamp (in seconds):
SELECT UNIX_TIMESTAMP(NOW());
SELECT UNIX_TIMESTAMP();
To get the timestamp column as a UNIX timestamp
SELECT UNIX_TIMESTAMP(`timestamp`) FROM `table_name`
To get a UTC datetime column as a UNIX timestamp
SELECT UNIX_TIMESTAMP(CONVERT_TZ(`utc_datetime`, '+00:00', ##session.time_zone)) FROM `table_name`
Get a current timezone datetime from a positive UNIX timestamp integer
SELECT FROM_UNIXTIME(`unix_timestamp_int`) FROM `table_name`
Get a UTC datetime from a UNIX timestamp
SELECT CONVERT_TZ(FROM_UNIXTIME(`unix_timestamp_int`), ##session.time_zone, '+00:00')
FROM `table_name`
Get a current timezone datetime from a negative UNIX timestamp integer
SELECT DATE_ADD('1970-01-01 00:00:00',INTERVAL -957632400 SECOND)
There are 3 places where the timezone might be set in MySQL:
Note: A timezone can be set in 2 formats:
an offset from UTC: '+00:00', '+10:00' or '-6:00'
as a named time zone: 'Europe/Helsinki', 'US/Eastern', or 'MET'
Named time zones can be used only if the time zone information tables
in the mysql database have been created and populated.
in the file "my.cnf"
default_time_zone='+00:00'
or
timezone='UTC'
##global.time_zone variable
To see what value they are set to
SELECT ##global.time_zone;
To set a value for it use either one:
SET GLOBAL time_zone = '+8:00';
SET GLOBAL time_zone = 'Europe/Helsinki';
SET ##global.time_zone='+00:00';
##session.time_zone variable
SELECT ##session.time_zone;
To set it use either one:
SET time_zone = 'Europe/Helsinki';
SET time_zone = "+00:00";
SET ##session.time_zone = "+00:00";
both "##global.time_zone variable" and "##session.time_zone variable" might return "SYSTEM" which means that they use the timezone set in "my.cnf".
For timezone names to work (even for default-time-zone) you must setup your timezone information tables need to be populated: http://dev.mysql.com/doc/refman/5.1/en/time-zone-support.html
Note: you can not do this as it will return NULL:
SELECT
CONVERT_TZ(`timestamp_field`, TIMEDIFF(NOW(), UTC_TIMESTAMP), '+00:00') AS `utc_datetime`
FROM `table_name`
Setup mysql timezone tables
For CONVERT_TZ to work, you need the timezone tables to be populated
SELECT * FROM mysql.`time_zone` ;
SELECT * FROM mysql.`time_zone_leap_second` ;
SELECT * FROM mysql.`time_zone_name` ;
SELECT * FROM mysql.`time_zone_transition` ;
SELECT * FROM mysql.`time_zone_transition_type` ;
If they are empty, then fill them up by running this command
mysql_tzinfo_to_sql /usr/share/zoneinfo | mysql -u root -p mysql
if this command gives you the error "data too long for column 'abbreviation' at row 1", then it might be caused by a NULL character being appended at the end of the timezone abbreviation
the fix being to run this
mysql_tzinfo_to_sql /usr/share/zoneinfo | mysql -u root -p mysql
(if the above gives error "data too long for column 'abbreviation' at row 1")
mysql_tzinfo_to_sql /usr/share/zoneinfo > /tmp/zut.sql
echo "SET SESSION SQL_MODE = '';" > /tmp/mysql_tzinfo_to.sql
cat /tmp/zut.sql >> /tmp/mysql_tzinfo_to.sql
mysql --defaults-file=/etc/mysql/my.cnf --user=verifiedscratch -p mysql < /tmp/mysql_tzinfo_to.sql
(make sure your servers dst rules are up to date zdump -v Europe/Moscow | grep 2011 https://chrisjean.com/updating-daylight-saving-time-on-linux/)
See the full DST (Daylight Saving Time) transition history for every timezone
SELECT
tzn.Name AS tz_name,
tztt.Abbreviation AS tz_abbr,
tztt.Is_DST AS is_dst,
tztt.`Offset` AS `offset`,
DATE_ADD('1970-01-01 00:00:00',INTERVAL tzt.Transition_time SECOND) AS transition_date
FROM mysql.`time_zone_transition` tzt
INNER JOIN mysql.`time_zone_transition_type` tztt USING(Time_zone_id, Transition_type_id)
INNER JOIN mysql.`time_zone_name` tzn USING(Time_zone_id)
-- WHERE tzn.Name LIKE 'Europe/Moscow' -- Moscow has weird DST changes
ORDER BY tzt.Transition_time ASC
CONVERT_TZ also applies any necessary DST changes based on the rules in the above tables and the date that you use.
Note:
According to the docs, the value you set for time_zone does not change, if you set it as "+01:00" for example, then the time_zone will be set as an offset from UTC, which does not follow DST, so it will stay the same all year round.
Only the named timezones will change time during daylight savings time.
Abbreviations like CET will always be a winter time and CEST will be summer time while +01:00 will always be UTC time + 1 hour and both won't change with DST.
The system timezone will be the timezone of the host machine where mysql is installed (unless mysql fails to determine it)
You can read more about working with DST here
When not to use UTC by the legendary Jon Skeet: https://codeblog.jonskeet.uk/2019/03/27/storing-utc-is-not-a-silver-bullet/
(For example a scheduled event in the future that represents a time, not an instant in time)
related questions:
How do I set the time zone of MySQL?
MySql - SELECT TimeStamp Column in UTC format
How to get Unix timestamp in MySQL from UTC time?
Converting Server MySQL TimeStamp To UTC
https://dba.stackexchange.com/questions/20217/mysql-set-utc-time-as-default-timestamp
How do I get the current time zone of MySQL?
MySQL datetime fields and daylight savings time -- how do I reference the "extra" hour?
Converting negative values from FROM_UNIXTIME
Sources:
https://bugs.mysql.com/bug.php?id=68861
http://dev.mysql.com/doc/refman/5.0/en/date-and-time-functions.html
http://dev.mysql.com/doc/refman/5.1/en/datetime.html
http://en.wikipedia.org/wiki/Coordinated_Universal_Time
http://shafiqissani.wordpress.com/2010/09/30/how-to-get-the-current-epoch-time-unix-timestamp/
https://web.ivy.net/~carton/rant/MySQL-timezones.txt
PHP and MySQL have their own default timezone configurations. You should synchronize time between your data base and web application, otherwise you could run some issues.
Read this tutorial: How To Synchronize Your PHP and MySQL Timezones
This is a working example:
jdbc:mysql://localhost:3306/database?useUnicode=yes&characterEncoding=UTF-8&serverTimezone=Europe/Moscow
The pros and cons are pretty much identical.It depends on whether you want this or not.
Be careful, if MySQL timezone differs from your system time (for instance PHP), comparing the time or printing to the user will involve some tinkering.
How about making your app agnostic of the server's timezone?
Owing to any of these possible scenarios:
You might not have control over the web/database server's timezone settings
You might mess up and set the settings incorrectly
There are so many settings as described in the other answers, and so many things to keep track of, that you might miss something
An update on the server, or a software reset, or another admin, might unknowing reset the servers' timezone to the default - thus breaking your application
All of the above scenarios give rise to breaking of your application's time calculations. Thus it appears that the better approach is to make your application work independent of the server's timezone.
The idea is simply to always create dates in UTC before storing them into the database, and always re-create them from the stored values in UTC as well. This way, the time calculations won't ever be incorrect, because they're always in UTC. This can be achieved by explicity stating the DateTimeZone parameter when creating a PHP DateTime object.
On the other hand, the client side functionality can be configured to convert all dates/times received from the server to the client's timezone. Libraries like moment.js make this super easy to do.
For example, when storing a date in the database, instead of using the NOW() function of MySQL, create the timestamp string in UTC as follows:
// Storing dates
$date = new DateTime('now', new DateTimeZone('UTC'));
$sql = 'insert into table_name (date_column) values ("' . $date . '")';
// Retreiving dates
$sql = 'select date_column from table_name where condition';
$dateInUTC = new DateTime($date_string_from_db, new DateTimeZone('UTC'));
You can set the default timezone in PHP for all dates created, thus eliminating the need to initialize the DateTimeZone class every time you want to create a date.
Check Timezone
SELECT ##system_time_zone as System_tz ,##global.time_zone as MYSQL_timeZone, NOW() as timenow_bymysql;
SET GLOBAL time_zone = '+05:30';
OR
change system time zone then restart MariaDB/MYSQL
and check again timezone
im storing the dates that entries were posted on in the db using a standard unix timestamp.
is it possible, using only a mysql query (no php logic), to select entries that were posted in a certain year?
id like to avoid retrieving ALL entries and then using php to filter on year value. i could store the year in a separate field of course, just curious about this
This should be what you're after:
SELECT FROM_UNIXTIME(my_unix_timestamp_column, '%Y') AS year FROM table_name WHERE my_unix_timestamp_column BETWEEN UNIX_TIMESTAMP('2004-01-01 00:00:00') AND UNIX_TIMESTAMP('2004-12-31 23:59:59');
You only want MySQL to do the hard work of extracting the year once:
SELECT your, columns
FROM posts
WHERE postdate BETWEEN UNIX_TIMESTAMP('20080101') AND (UNIX_TIMESTAMP('20090101')-1)
Obviously, this adapts easily to extract posts within a certain month or day or decade etc.
maybe use the FROM_UNIXTIME() function
http://dev.mysql.com/doc/refman/5.1/en/date-and-time-functions.html
http://dev.mysql.com/doc/refman/5.1/en/date-and-time-functions.html#function_from-unixtime
A better way to do that is to use a little bit of PHP to create the unix timestamp you want. If it is this year try
$timestamp = strtotime("January, 1, 2009");
$db->query("Select * from table where time < $timestamp");
This is just an example, but you will be able to quickly narrow your results and only do very minimal php logic.
Depends of your mysql version. 5.1 has this neat function FROM_UNIXTIME(unix_timestamp,format)
mysql> SELECT FROM_UNIXTIME(UNIX_TIMESTAMP(),
-> '%Y %D %M %h:%i:%s %x');
-> '2007 30th November 10:30:59 2007'