The Ultimate Guide to High Availability with MariaDB

DATETIME

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Contents

  1. Syntax
  2. Description
  3. Supported Values
  4. Oracle Mode
  5. Internal Format
  6. Examples
  7. See Also

Syntax

DATETIME [(microsecond precision)]

Description

A date and time combination.

MariaDB displays DATETIME values in 'YYYY-MM-DD HH:MM:SS.ffffff' format, but allows assignment of values to DATETIME columns using either strings or numbers. For details, see date and time literals.

DATETIME columns also accept CURRENT_TIMESTAMP as the default value.

MariaDB 10.1.2 introduced the --mysql56-temporal-format option, on by default, which allows MariaDB to store DATETMEs using the same low-level format MySQL 5.6 uses. For more information, see Internal Format, below.

For storage requirements, see Data Type Storage Requirements.

Supported Values

MariaDB stores values that use the DATETIME data type in a format that supports values between 1000-01-01 00:00:00.000000 and 9999-12-31 23:59:59.999999.

MariaDB can also store microseconds with a precision between 0 and 6. If no microsecond precision is specified, then 0 is used by default.

MariaDB also supports '0000-00-00' as a special zero-date value, unless NO_ZERO_DATE is specified in the SQL_MODE. Similarly, individual components of a date can be set to 0 (for example: '2015-00-12'), unless NO_ZERO_IN_DATE is specified in the SQL_MODE. In many cases, the result of en expression involving a zero-date, or a date with zero-parts, is NULL. If the ALLOW_INVALID_DATES SQL_MODE is enabled, if the day part is in the range between 1 and 31, the date does not produce any error, even for months that have less than 31 days.

Oracle Mode

In Oracle mode, DATE with a time portion is a synonym for DATETIME. See also mariadb_schema.

Internal Format

In MariaDB 10.1.2 a new temporal format was introduced from MySQL 5.6 that alters how the TIME, DATETIME and TIMESTAMP columns operate at lower levels. These changes allow these temporal data types to have fractional parts and negative values. You can disable this feature using the mysql56_temporal_format system variable.

Tables that include TIMESTAMP values that were created on an older version of MariaDB or that were created while the mysql56_temporal_format system variable was disabled continue to store data using the older data type format.

In order to update table columns from the older format to the newer format, execute an ALTER TABLE... MODIFY COLUMN statement that changes the column to the *same* data type. This change may be needed if you want to export the table's tablespace and import it onto a server that has mysql56_temporal_format=ON set (see MDEV-15225).

For instance, if you have a DATETIME column in your table: 

SHOW VARIABLES LIKE 'mysql56_temporal_format';

+-------------------------+-------+
| Variable_name           | Value |
+-------------------------+-------+
| mysql56_temporal_format | ON    |
+-------------------------+-------+

ALTER TABLE example_table MODIFY ts_col DATETIME;

When MariaDB executes the ALTER TABLE statement, it converts the data from the older temporal format to the newer one.

In the event that you have several tables and columns using temporal data types that you want to switch over to the new format, make sure the system variable is enabled, then perform a dump and restore using mysqldump. The columns using relevant temporal data types are restored using the new temporal format.

Starting from MariaDB 10.5.1 columns with old temporal formats are marked with a /* mariadb-5.3 */ comment in the output of SHOW CREATE TABLE, SHOW COLUMNS, DESCRIBE statements, as well as in the COLUMN_TYPE column of the INFORMATION_SCHEMA.COLUMNS Table.

SHOW CREATE TABLE mariadb5312_datetime\G
*************************** 1. row ***************************
       Table: mariadb5312_datetime
Create Table: CREATE TABLE `mariadb5312_datetime` (
  `dt0` datetime /* mariadb-5.3 */ DEFAULT NULL,
  `dt6` datetime(6) /* mariadb-5.3 */ DEFAULT NULL
) ENGINE=MyISAM DEFAULT CHARSET=latin1

Examples

CREATE TABLE t1 (d DATETIME);

INSERT INTO t1 VALUES ("2011-03-11"), ("2012-04-19 13:08:22"),
 ("2013-07-18 13:44:22.123456");

SELECT * FROM t1;
+---------------------+
| d                   |
+---------------------+
| 2011-03-11 00:00:00 |
| 2012-04-19 13:08:22 |
| 2013-07-18 13:44:22 |
+---------------------+

CREATE TABLE t2 (d DATETIME(6));

INSERT INTO t2 VALUES ("2011-03-11"), ("2012-04-19 13:08:22"),
 ("2013-07-18 13:44:22.123456");

SELECT * FROM t2;
+----------------------------+
| d                          |
+----------------------------+
| 2011-03-11 00:00:00.000000 |
| 2012-04-19 13:08:22.000000 |
| 2013-07-18 13:44:22.123456 |
+----------------------------++

Strings used in datetime context are automatically converted to datetime(6). If you want to have a datetime without seconds, you should use CONVERT(..,datetime).

SELECT CONVERT('2007-11-30 10:30:19',datetime);
+-----------------------------------------+
| CONVERT('2007-11-30 10:30:19',datetime) |
+-----------------------------------------+
| 2007-11-30 10:30:19                     |
+-----------------------------------------+

SELECT CONVERT('2007-11-30 10:30:19',datetime(6));
+--------------------------------------------+
| CONVERT('2007-11-30 10:30:19',datetime(6)) |
+--------------------------------------------+
| 2007-11-30 10:30:19.000000                 |
+--------------------------------------------+

See Also

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