Skip to content

Latest commit

 

History

History
262 lines (184 loc) · 13.8 KB

data-type-date-and-time.md

File metadata and controls

262 lines (184 loc) · 13.8 KB
Raw
title summary aliases
Date and Time Types
Learn about the supported date and time types.
/docs/dev/data-type-date-and-time/
/docs/dev/reference/sql/data-types/date-and-time/

Date and Time Types

TiDB supports all MySQL date and time data types to store temporal values: DATE, TIME, DATETIME, TIMESTAMP, and YEAR. For more information, see Date and Time Data Types in MySQL.

Each of these types has its range of valid values, and uses a zero value to indicate that it is an invalid value. In addition, the TIMESTAMP and DATETIME types can automatically generate new time values on modification.

When dealing with date and time value types, note:

  • Although TiDB tries to interpret different formats, the date-portion must be in the format of year-month-day (for example, '1998-09-04'), rather than month-day-year or day-month-year.

  • If the year-portion of a date is specified as 2 digits, TiDB converts it based on specific rules.

  • If a numeric value is needed in the context, TiDB automatically converts the date or time value into a numeric type. For example:

    mysql> SELECT NOW(), NOW()+0, NOW(3)+0;
+---------------------+----------------+--------------------+
| NOW()               | NOW()+0        | NOW(3)+0           |
+---------------------+----------------+--------------------+
| 2012-08-15 09:28:00 | 20120815092800 | 20120815092800.889 |
+---------------------+----------------+--------------------+

  • TiDB might automatically convert invalid values or values beyond the supported range to a zero value of that type. This behavior is dependent on the SQL Mode set. For example:

    mysql> show create table t1;
+-------+---------------------------------------------------------------------------------------------------------+
| Table | Create Table                                                                                            |
+-------+---------------------------------------------------------------------------------------------------------+
| t1    | CREATE TABLE `t1` (
  `a` time DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin |
+-------+---------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

mysql> select @@sql_mode;
+-------------------------------------------------------------------------------------------------------------------------------------------+
| @@sql_mode                                                                                                                                |
+-------------------------------------------------------------------------------------------------------------------------------------------+
| ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION |
+-------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

mysql> insert into t1 values ('2090-11-32:22:33:44');
ERROR 1292 (22007): Truncated incorrect time value: '2090-11-32:22:33:44'
mysql> set @@sql_mode='';                                                                                                                                                                                                                     Query OK, 0 rows affected (0.01 sec)

mysql> insert into t1 values ('2090-11-32:22:33:44');
Query OK, 1 row affected, 1 warning (0.01 sec)

mysql> select * from t1;
+----------+
| a        |
+----------+
| 00:00:00 |
+----------+
1 row in set (0.01 sec)

  • Setting different SQL modes can change TiDB behaviors.

  • If the SQL mode NO_ZERO_DATE is not enabled, TiDB allows month or day in the columns of DATE and DATETIME to be zero value, for example, '2009-00-00' or '2009-01-00'. If this date type is to be calculated in a function, for example, in DATE_SUB() or DATE_ADD(), the result can be incorrect.

  • By default, TiDB enables the SQL mode NO_ZERO_DATE. This mode prevents storing zero values such as '0000-00-00'.

Different types of zero value are shown in the following table:

Date Type "Zero" Value
DATE '0000-00-00'
TIME '00:00:00'
DATETIME '0000-00-00 00:00:00'
TIMESTAMP '0000-00-00 00:00:00'
YEAR 0000

Invalid DATE, DATETIME, TIMESTAMP values are automatically converted to the corresponding type of zero value ( '0000-00-00' or '0000-00-00 00:00:00' ) if the SQL mode permits such usage.

Supported types

DATE type

DATE only contains date-portion and no time-portion, displayed in YYYY-MM-DD format. The supported range is '0000-01-01' to '9999-12-31':

DATE

TIME type

For the TIME type, the format is HH:MM:SS[.fraction] and valid values range from '-838:59:59.000000' to '838:59:59.000000'. TIME is used not only to indicate the time within a day but also to indicate the time interval between 2 events. An optional fsp value in the range from 0 to 6 may be given to specify fractional seconds precision. If omitted, the default precision is 0:

TIME[(fsp)]

Note:

Pay attention to the abbreviated form of TIME. For example, '11:12' means '11:12:00' instead of '00:11:12'. However, '1112' means '00:11:12'. These differences are caused by the presence or absence of the : character.

DATETIME type

DATETIME contains both date-portion and time-portion. Valid values range from '0000-01-01 00:00:00.000000' to '9999-12-31 23:59:59.999999'.

TiDB displays DATETIME values in YYYY-MM-DD HH:MM:SS[.fraction] format, but permits assignment of values to DATETIME columns using either strings or numbers. An optional fsp value in the range from 0 to 6 may be given to specify fractional seconds precision. If omitted, the default precision is 0:

DATETIME[(fsp)]

TIMESTAMP type

TIMESTAMP contains both date-portion and time-portion. Valid values range from '1970-01-01 00:00:01.000000' to '2038-01-19 03:14:07.999999' in UTC time. An optional fsp value in the range from 0 to 6 may be given to specify fractional seconds precision. If omitted, the default precision is 0.

In TIMESTAMP, zero is not permitted to appear in the month-portion or day-portion. The only exception is zero value itself '0000-00-00 00:00:00'.

TIMESTAMP[(fsp)]

Timezone Handling

When TIMESTAMP is to be stored, TiDB converts the TIMESTAMP value from the current time zone to UTC time zone. When TIMESTAMP is to be retrieved, TiDB converts the stored TIMESTAMP value from UTC time zone to the current time zone (Note: DATETIME is not handled in this way). The default time zone for each connection is the server's local time zone, which can be modified by the environment variable time_zone.

Warning:

As in MySQL, the TIMESTAMP data type suffers from the Year 2038 Problem. For storing values that may span beyond 2038, please consider using the DATETIME type instead.

YEAR type

The YEAR type is specified in the format 'YYYY'. Supported values range from 1901 to 2155, or the zero value of 0000:

YEAR[(4)]

YEAR follows the following format rules:

  • Four-digit numeral ranges from 1901 to 2155
  • Four-digit string ranges from '1901' to '2155'
  • One-digit or two-digit numeral ranges from 1 to 99. Accordingly, 1-69 is converted to 2001-2069 and 70-99 is converted to 1970-1999
  • One-digit or two-digit string ranges from '0' to '99'
  • Value 0 is taken as 0000 whereas the string '0' or '00' is taken as 2000

Invalid YEAR value is automatically converted to 0000 (if users are not using the NO_ZERO_DATE SQL mode).

Automatic initialization and update of TIMESTAMP and DATETIME

Columns with TIMESTAMP or DATETIME value type can be automatically initialized or updated to the current time.

For any column with TIMESTAMP or DATETIME value type in the table, you can set the default or auto-update value as current timestamp.

These properties can be set by setting DEFAULT CURRENT_TIMESTAMP and ON UPDATE CURRENT_TIMESTAMP when the column is being defined. DEFAULT can also be set as a specific value, such as DEFAULT 0 or DEFAULT '2000-01-01 00:00:00'.

CREATE TABLE t1 (
    ts TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
    dt DATETIME DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
);

The default value for DATETIME is NULL unless it is specified as NOT NULL. For the latter situation, if no default value is set, the default value is be 0.

CREATE TABLE t1 (
    dt1 DATETIME ON UPDATE CURRENT_TIMESTAMP,         -- default NULL
    dt2 DATETIME NOT NULL ON UPDATE CURRENT_TIMESTAMP -- default 0
);

Decimal part of time value

DATETIME and TIMESTAMP values can contain a fractional part of up to 6 digits which is accurate to microseconds. In any column of DATETIME or TIMESTAMP types, a fractional part is stored instead of being discarded. With a fractional part, the value is in the format of 'YYYY-MM-DD HH:MM:SS[.fraction]', and the fraction ranges from 000000 to 999999. A decimal point must be used to separate the fraction from the rest.

  • Use type_name(fsp) to define a column that supports fractional precision, where type_name can be TIME, DATETIME or TIMESTAMP. For example,

    CREATE TABLE t1 (t TIME(3), dt DATETIME(6));

    fsp must range from 0 to 6.

    0 means there is no fractional part. If fsp is omitted, the default is 0.

  • When inserting TIME, DATETIME or TIMESTAMP which contain a fractional part, if the number of digit of the fraction is too few, or too many, rounding might be needed in the situation. For example:

    mysql> CREATE TABLE fractest( c1 TIME(2), c2 DATETIME(2), c3 TIMESTAMP(2) );
Query OK, 0 rows affected (0.33 sec)

mysql> INSERT INTO fractest VALUES
     > ('17:51:04.777', '2014-09-08 17:51:04.777',   '2014-09-08 17:51:04.777');
Query OK, 1 row affected (0.03 sec)

mysql> SELECT * FROM fractest;
+-------------|------------------------|------------------------+
| c1          | c2                     | c3                     |
+-------------|------------------------|------------------------+
| 17:51:04.78 | 2014-09-08 17:51:04.78 | 2014-09-08 17:51:04.78 |
+-------------|------------------------|------------------------+
1 row in set (0.00 sec)

Conversions between date and time types

Sometimes we need to make conversions between date and time types. But some conversions might lead to information loss. For example, DATE, DATETIME and TIMESTAMP values all have their own respective ranges. TIMESTAMP should be no earlier than the year 1970 in UTC time or no later than UTC time '2038-01-19 03:14:07'. Based on this rule, '1968-01-01' is a valid date value of DATE or DATETIME, but becomes 0 when it is converted to TIMESTAMP.

The conversions of DATE:

  • When DATE is converted to DATETIME or TIMESTAMP, a time-portion '00:00:00' is added, because DATE does not contain any time information
  • When DATE is converted to TIME, the result is '00:00:00'

Conversions of DATETIME or TIMESTAMP:

  • When DATETIME or TIMESTAMP is converted to DATE, the time and fractional part is discarded. For example, '1999-12-31 23:59:59.499' is converted to '1999-12-31'
  • When DATETIME or TIMESTAMP is converted to TIME, the date-portion is discarded, because TIME does not contain any date information

When we convert TIME to other time and date formats, the date-portion is automatically specified as CURRENT_DATE(). The final converted result is a date that consists of TIME and CURRENT_DATE(). This is to say that if the value of TIME is beyond the range from '00:00:00' to '23:59:59', the converted date-portion does not indicate the current day.

When TIME is converted to DATE, the process is similar, and the time-portion is discarded.

Using the CAST() function can explicitly convert a value to a DATE type. For example:

date_col = CAST(datetime_col AS DATE)

Converting TIME and DATETIME to numeric format. For example:

mysql> SELECT CURTIME(), CURTIME()+0, CURTIME(3)+0;
+-----------|-------------|--------------+
| CURTIME() | CURTIME()+0 | CURTIME(3)+0 |
+-----------|-------------|--------------+
| 09:28:00  |       92800 |    92800.887 |
+-----------|-------------|--------------+
mysql> SELECT NOW(), NOW()+0, NOW(3)+0;
+---------------------|----------------|--------------------+
| NOW()               | NOW()+0        | NOW(3)+0           |
+---------------------|----------------|--------------------+
| 2012-08-15 09:28:00 | 20120815092800 | 20120815092800.889 |
+---------------------|----------------|--------------------+

Two-digit year-portion contained in the date

The two-digit year-portion contained in date does not explicitly indicate the actual year and is ambiguous.

For DATETIME, DATE and TIMESTAMP types, TiDB follows the following rules to eliminate ambiguity:

  • Values between 01 and 69 is converted to a value between 2001 and 2069
  • Values between 70 and 99 is converted to a value between 1970 and 1999

These rules also apply to the YEAR type, with one exception:

When numeral 00 is inserted to YEAR(4), the result is 0000 rather than 2000.

If you want the result to be 2000, specify the value to be 2000.

The two-digit year-portion might not be properly calculated in some functions such MIN() and MAX(). For these functions, the four-digit format suites better.