Date and Time Data Types
Date and time data types include the following:
• Date data types
• Time data types
• Timestamp data types
• Interval data types
Date and Time Input Formats
Date/time data values have the following data type input formats:
• Ansidate
• Ingresdate
• Time (without time zone)
• Time with time zone
• Time with local time zone
• Timestamp (without time zone)
• Timestamp with time zone
• Timestamp with local time zone
• Interval year to month
• Interval day to second
Date Data Type
The declaration format of the date type can be one of the following:
DATE
ANSIDATE
INGRESDATE
Examples:
Time Data Types
The TIME data type consists of a time in hour, minutes, seconds, optional fractions of a second, and optional time zone.
The format is as follows:
TIME [time_precision] [time_zone_spec]
time_precision
(Optional) Indicates the number of digits of precision in the fractions of seconds, as an integer value from 0 to 9. When no time precision is supplied, the value of time_precision is set to 0 by default.
Note: When a value is entered that exceeds the specified precision, the value is truncated at the specified precision.
time_zone_spec
(Optional) Specifies a time zone as one of the following:
• WITH TIME ZONE
• WITHOUT TIME ZONE
• WITH LOCAL TIME ZONE
Note: The time value in TIME WITH TIME ZONE data type indicates the time at the specified time zone.
Examples:
Timestamp Data Types
The TIMESTAMP data type consists of a date and time, with optional time zone.
The format is as follows:
TIMESTAMP [(timestamp_precision)] [time_zone_spec]
timestamp_precision
(Optional) Indicates the number of digits of precision in the fractions of seconds, as an integer value from 0 to 9. The default is 6.
Note: When a value is entered that exceeds the specified precision, the value is truncated at the specified precision.
time_zone_spec
(Optional) Specifies a time zone as one of the following:
• WITH TIME ZONE
• WITHOUT TIME ZONE
• WITH LOCAL TIME ZONE
Note: The time value in TIMESTAMP WITH TIME ZONE data type indicates the time at the specified time zone.
Examples:
Note: Two TIMESTAMP WITH TIME ZONE values are considered identical if they represent the same instant in UTC, regardless of the TIME ZONE offsets stored in the database. For example:
TIMESTAMP '2006-12-15 9:30:55 -8:00'
is the same as
TIMESTAMP '2006-12-15 12:30:55 -5:00'
Interval Data Types
The INTERVAL data types include year to month and day to second intervals.
The format is as follows:
INTERVAL interval_qualifier
interval_qualifier
Defines an interval column as one of the following:
• YEAR TO MONTH
• DAY TO SECOND [(second_precision)]
where second_precision is the number of digits in the fractions of seconds field.
Note: When a value is entered that exceeds the specified precision, the value is truncated at the specified precision.
Examples:
Summary of ANSI Date/Time Data Types
The following table summarizes valid input and output formats for ANSI date/time data types:
where:
yyyy
Is a four-digit year value. All four digits are required.
mm
Is a two-digit month value between 01 to 12.
dd
Is a two-digit day value between 01 to 31.
hh
Is a two-digit hour value between 00 to 23.
nn
Is a two-digit minute value between 00 to 59.
th
Is a two-digit hour value between -12 to +14.
tm
Is a two-digit minute value between 00 to 59.
years
Is the number of years. Maximum of 9999.
days
Is the number of days. Maximum of 3652047.
ss
Is a two-digit seconds value between 0 and 59.
ffff...
Is 1 to 9 digits fractions of a second.
Ingresdate Data Types
The ingresdate data type is an abstract data type. The ingresdate data type input formats are as follows:
• Absolute date
• Absolute time
• Combined date and time
• Time interval
Note: The ingresdate type is not supported in X100 tables.
Ingresdate Input
Ingresdate values are specified as quoted character strings. A date can be entered by itself or with a time value. If a date is entered without the time, no time is shown when the data
displays (see page
How Ingres Dates and Times Are Displayed).
Because ingresdate can store different forms of date, time, and interval information, the nature of the value is determined by the input format.
Ingresdate absolute formats recognized are determined by the active date format, which can be altered to suit particular country preferences.
Ingresdate interval forms follow a simple form that is distinct from the absolute forms.
II_DATE_FORMAT for Absolute Ingresdate
The II_DATE_FORMAT setting determines the legal formats for absolute ingresdate values. The default setting is US.
II_DATE_FORMAT can be set on a session basis. For information on setting II_DATE_FORMAT, see the System Administrator Guide.
The following table lists ingresdate input and output formats:
Year defaults to the current year. In formats that include delimiters (such as forward slashes or dashes), specify the last two digits of the year; the first two digits default to the current century (2000). For example, if this date is entered:
'03/21/03'
using the format mm/dd/yyyy, the DBMS Server assumes that you are referring to March 21, 2003.
In three-character month formats, for example, dd-mmm-yy, specify three-letter abbreviations for the month (for example, mar, apr, may).
To specify the current system date, use the constant, today. For example:
SELECT DATE('TODAY');
To specify the current system date and time, use the constant, now.
For convenience, the ANSI date/time formats are also accepted as input to ingresdates.
II_DATE_CENTURY_BOUNDARY for Absolute Ingresdate
The II_DATE_CENTURY_BOUNDARY variable, which can be set to an integer in the 0< n <=100 range, dictates the implied century for an ingresdate value when only the last two digits of the year are entered.
For example, if II_DATE_CENTURY_BOUNDARY is 50 and the current year is 1999, an input date of 3/17/51 is treated as March 17, 1951, but a date of 03/17/49 is treated as March 17, 2049.
If the II_DATE_CENTURY_BOUNDARY variable is not set or if it is set to 0 or 100, the current century is used. If the user enters the full four digits for the year in a four-digit year field in the application, the year is accepted as entered, regardless of the II_DATE_CENTURY_BOUNDARY setting.
Absolute Time Input for Ingresdate
The format for inputting an absolute time into an ingresdate value is:
'hh:mm[:ss] [am|pm] [timezone]'
Input formats for absolute times are assumed to be on a 24-hour clock. If a time with the designation am or pm is entered, the time is converted to a 24-hour internal and displayed representation.
If timezone is omitted, the local time zone designation is assumed. Times are stored as Greenwich Mean Time (GMT) and displayed using the time zone adjustment specified by II_TIMEZONE_NAME.
If an absolute time without a date is entered, the date defaults to the current system date.
Combined Date and Time Input for Ingresdate
Any valid absolute date input format can be paired with a valid absolute time input format to form a valid date and time entry in an ingresdate. The following table shows examples of valid date and time entries, using the US absolute date input formats:
Interval Input for Ingresdate
Ingres interval data includes date intervals, time intervals, or a combination.
An ingresdate interval value is entered as a quoted string of qualified numbers that mark the units of the interval. For example 18 months might be represented as:
'1 year 6 months'
The interval syntax is of the form:
'[ n YEARS][ n MONTHS][ n DAYS][ n HOURS][ n MINUTES][n SECONDS]'
where n can be a positive or negative integer. The interval qualifiers can be abbreviated:
Here are example date intervals:
'5 years'
'8 months'
'14 days'
'5 yrs 8 mos 14 days'
'5 years 8 months'
'5 years 14 days'
'8 months 14 days'
Here are example time intervals:
'23 hours'
'38 minutes'
'53 seconds'
'23 hrs 38 mins 53 secs'
'23 hrs 53 seconds'
'28 hrs 38 mins'
'38 mins 53 secs'
'23:38 hours'
'23:38:53 hours'
If a time interval greater than 1 day is entered, the interval is converted to a date and time interval. For example:
'26 hours'
is converted to:
'1 day 2 hours'
Valid ranges for Ingres date and time intervals are:
For convenience, the ANSI interval input formats can also be used for loading ingresdate intervals.
How Ingres Dates and Times Are Displayed
Absolute Dates
By default ingresdate absolute values (date, time, or timestamp) are displayed as strings of left-justified 25 characters with trailing blanks.
The display format for an absolute ingresdate is determined by the
II_DATE_FORMAT (see page
II_DATE_FORMAT for Absolute Ingresdate) or the SQL statement
SET DATE_FORMAT (see page
Date_format on page 735).
The display format for an absolute time is:
hh:mm:ss
The DBMS Server displays 24-hour times for the current time zone. Times are stored as Greenwich Mean Time (GMT) and displayed using the time zone adjustment specified by II_TIMEZONE_NAME.
If a date is not entered when entering a time, the current date is inserted in the date place. If seconds are not entered when entering a time, zeros display in the seconds place.
Intervals
By default ingresdate interval is displayed as the first 25 characters of the interval string; the remainder of the interval will be truncated. The maximum length of an ingresdate interval is 57 characters.
The complete format appears as:
[-]yy yrs [-]mm mos [-]dd days [-]hh hrs [-]mm mins [-]ss secs
What is stored in the ingresdate interval determines what is displayed in the 25 characters. By default the "least significant" portion is truncated to fit the result into the 25 characters. What is deemed as "least significant" is a function of the size of any component of the time interval. Trailing blanks are appended to fill out the string to 25 characters.
For example, if the following ingresdate interval had been inserted into an ingresdate column:
5 yrs 4 mos 3 days 12 hrs 32 min 14 secs
when selected within terminal monitor, by default, the following would be returned:
5 yrs 4 mos 3 days 12 hrs
The least significant portion of the interval, minutes and seconds, have been lost due to truncation to fit the result into 25 characters. This happens silently—there are no warnings or error messages.
To display the full string, it is necessary to cast the column to a character string of the required length. For example:
CHAR(my_interval,60)
returns the full value plus trailing spaces to the length specified in the cast:
5 yrs 4 mos 3 days 12 hrs 32 min 14 secs
Coercion Between Date/Time Data Types
The rules governing coercion between the various date/time data types are as follows:
1. Ansidate cannot be converted to any of the time types, nor can the time types be converted to ansidate. Doing so results in error E_AD5066_DATE_COERCION.
2. When converting from a data type that does not have time zone information to a data type with time zone value (for example, ansidate to a timestamp with time zone, time without time zone to a time with time zone), the time zone is set to the current session time zone.
Example: In Eastern Standard Time (EST) time zone (that is, -05:00), the following statements insert a value of 2007-02-08 16:41:00-05:00 in the database.
CREATE TABLE tab (col1 TIMESTAMP WITH TIME ZONE);
INSERT INTO tab VALUES (TIMESTAMP ‘2007-02-08 16:41:00’);
3. Ingresdate, time with local time zone, and timestamp with local time zone, store date/time values in UTC. When converting from other data types like ansidate, time with/without time zone, timestamp with/without time zone to these data types, the session time zone displacement is subtracted from the date/time value. On the reverse operation, when converting from ansidate, time with/without time zone, timestamp with/without time zone to ingresdate, time with local time zone and timestamp with local time zone, the session time zone displacement is added to the date/time value in the database to make it in local time zone.
Example: In EST time zone (with time zone displacement of -05 :00), the following query stores a value of 2007-02-18 15:04:12 in the database:
CREATE TABLE tab (col1 TIMESTAMP WITH LOCAL TIME ZONE);
INSERT INTO tab VALUES (TIMESTAMP ‘2007-02-18 10:04:12’);
If this value was selected in PST time zone (with time zone displacement of -08:00), the session time zone value is added to the value stored in database and the value in local time zone is displayed, that is:
2007-02-18 07:04:12
4. When a time value is converted to a timestamp, date, or time/timestamp with local time zone types, the year, month, and day fields are filled with the current year, month, and day value.
Example: If current date is 08 Feb 2007 then the following statements insert a value of 2007-02-08 17:01:00 in the database:
CREATE TABLE tab (col1 TIMESTAMP);
INSERT INTO tab VALUES (TIME ’17:01:00’);
5. When converting from time without time zone to time with local time zone, the following procedure is used:
a. Current date is added to the time value to make a timestamp.
b. Time zone displacement is then applied to the time value.
c. The date part is removed from the result.
Example: If current date is 08 Feb 2007 and the session time zone is -05 :00 (EST), the following query stores a value of 22:01:00 in the database:
CREATE TABLE tab (col1 TIME WITH LOCAL TIME ZONE);
INSERT INTO tab VALUES (TIME ’17:01:00’);
6. INTERVAL types cannot be converted to any other types except themselves and ingresdates.
7. When a time/timestamp with time zone is converted to ingresdate, time with local time zone, or timestamp with local time zone, the time value is converted to UTC by applying the time zone information in the value.
Example: In any time zone, the following query will insert a value of 2007-02-18 03:04:12 in the database:
CREATE TABLE tab (col1 TIMESTAMP WITH LOCAL TIME ZONE);
INSERT INTO tab VALUES (TIMESTAMP ‘2007-02-18 10:04:12-07:00’);