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Displaying posts with tag: time (reset)
MySQL auto update date_created and date_updated columns

It's usually a good practice to have two columns called date_created and date_updated in every table. One can always use it in application and it helps in debugging too as to when a record was created and last updated in various circumstances and contexts.




This responsibility can be given to MySQL to automatically assign current time values to these columns.

In MySQL 5.6 onwards, this can be done by setting the data type of the columns to be either date time or timestamp and creating date_created column with NOT NULL DEFAULT CURRENT_TIMESTAMP  schema and date_updated column with NOT NULL DEFAULT '0000-00-00 00:00:00' as schema with attribute ON UPDATE CURRENT_TIMESTAMP.

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Upgrading to MySQL 5.7, focusing on temporal types

In this post, we’ll discuss how MySQL 5.7 handles the old temporal types during an upgrade.

MySQL changed the temporal types in MySQL 5.6.4, and it introduced a new feature: microseconds resolution in the TIME, TIMESTAMP and DATETIME types. Now these parameters can be set down to microsecond granularity. Obviously, this means format changes, but why is this important?

Are they converted automatically to the new format?

If we had tables in MySQL 5.5 that used TIME, TIMESTAMP or DATETIME are these fields are going to be converted to the new format when upgrading to 5.6? The answer is “NO.” Even if we …

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Which Compression Tool Should I Use for my Database Backups? (Part I: Compression)

This week we are talking about size, which is a subject that should matter to any system administrator in charge of the backup system of any project, and in particular database backups.

I sometimes get questions about what should be the best compression tool to apply during a particular backup system: gzip? bzip2? any other?

The testing environment

In order to test several formats and tools, I created a .csv file (comma-separated values) that was 3,700,635,579 bytes in size by transforming a recent dump of all the OpenStreetMap nodes of the European portion of Spain. It had a total of 46,741,126 rows and looked like this:

171773  38.6048402      -0.0489871      4       2012-08-25 00:37:46     12850816        472193  rubensd
171774  38.6061981      -0.0496867      2       2008-01-19 10:23:21     666916  9250 …
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Recovering temporal types in MySQL 5.6: TIME, TIMESTAMP and DATETIME

MySQL 5.6 introduces a new feature – microseconds resolution in some temporal types. As of 5.6.4 TIME, TIMESTAMP and DATETIME can have a fractional part. To create a field with subseconds you can specify precision in brackets: TIME(3), DATETIME(6) etc.

Obviously, the new feature requires the format change. All three types may now have a tail with a fractional part. The tail may be one, two or three bytes long and can store up to six digits after the point.

The non-fractional part has changed too. Thus, DATETIME uses only five bytes comparing to eight in previous versions.

As of revision 79 the …

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Converting Timezone-Specific Times in MySQL

Twice last week, a developer wanted to convert the existing datetime values in a database to UTC. The datetime values were the default for the server, which was the US/Pacific time zone, which is subject to Daylight Saving Time changes. Both developers for both applications wanted to convert all the times to UTC, so there would not be any changes due to Daylight Saving Time, and asked me for an easy query to know which times should be changed by adding 7 hours and which times should have 8 hours added to them.

The good news is that MySQL has some built-in functionality to make this easier. You may know about the CONVERT_TZ() function in MySQL, and that you can use it in a query to convert times like this:

mysql> SELECT CONVERT_TZ(NOW(),'-8:00','-0:00');
+-----------------------------------+
| …

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Retrieve time period like facebook fashion

In facebook stream you’ll see the time period at the bottom of the stream. For example: 4 minutes ago, 2 days ago, 3 weeks ago…. In our recent project we have to show similar time fashion for our application’s activity stream. So I write a function to retrieve the time duration. In our mysql database, [...]


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Detecting invalid and zero temporal values

I’ve been thinking a lot about invalid and zero temporal values and how to detect them with MySQL date and time functions because mk-table-checksum has to handle “everything” correctly and efficiently. The requirements are complex because we have to take into account what MySQL allows to be stored verses what it allows to be used in certain operations and functions, how it sorts a mix of real and invalid temporal values for MIN() and MAX(), how to detect a temporal value as equivalent to zero, and how different MySQL versions might affect any of the aforementioned.

At base, the four guiding requirements are:

  1. Detect and discard invalid time, date, and datetime values
  2. Detect zero-equivalent temporal values
  3. Do #1 and #2 using only MySQL functions
  4. Work in MySQL 4.0 …
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MySQL query that get ranks today, this week and this month

In this article I’m showing how to retrieve result based on today, week and month using mysql query. To learn the techniques just visit http://thinkdiff.net/mysql/getting-rank-today-this-week-and-this-month/


Getting rank today, this week and this month

In my previous article I’ve shown how to get rank using mysql query. Now I’m showing how to retrieve result based on today, week and month using mysql query. Actually I also implemented this in my quiz project so I’m sharing this with you.

For the table structure please look my previous article http://thinkdiff.net/mysql/how-to-get-rank-using-mysql-query/

Task 1: I’ve to retrieve those users rank who played the game today.
Solution: Look at the query

SELECT uid, participated, correct, wrong from quiz_user
    WHERE DAYOFMONTH(CURDATE())=extract(day from updated)
    ORDER BY correct DESC, participated ASC
    limit 30

So the above query returns the result of those users who played today. Here

CURDATE() …
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Follow-up To Loading CSS And JS Conditionally

First of all, I'd like to thank everyone who read and gave their 2 cents about the [WordPress Plugin Development] How To Include CSS and JavaScript Conditionally And Only When Needed By The Posts post. The article was well received and will hopefully spark some optimizations around loading styles and scripts.

Here are some discussions and mentions around the web:

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