Date/time literals

• 1: Time zone values
• 2: Day of the week names
• 3: Month names
• 4: Interval literal
• 4.1: Interval subtype units
• 4.2: Interval qualifier

1 - Time zone values

Vertica attempts to be compatible with the SQL standard definitions for time zones. However, the SQL standard has an odd mix of date and time types and capabilities. Obvious problems are:

• Although the DATE type does not have an associated time zone, the TIME type can. Time zones in the real world have little meaning unless associated with a date as well as a time, since the offset can vary through the year with daylight-saving time boundaries.

• Vertica assumes your local time zone for any data type containing only date or time.

• The default time zone is specified as a constant numeric offset from UTC. It is therefore not possible to adapt to daylight-saving time when doing date/time arithmetic across DST boundaries.

To address these difficulties, OpenText recommends using Date/Time types that contain both date and time when you use time zones. OpenText recommends that you do not use the type TIME WITH TIME ZONE, even though it is supported it for legacy applications and for compliance with the SQL standard.

Time zones and time-zone conventions are influenced by political decisions, not just earth geometry. Time zones around the world became somewhat standardized during the 1900's, but continue to be prone to arbitrary changes, particularly with respect to daylight-savings rules.

Vertica currently supports daylight-savings rules over the time period 1902 through 2038, corresponding to the full range of conventional UNIX system time. Times outside that range are taken to be in "standard time" for the selected time zone, no matter what part of the year in which they occur.

2 - Day of the week names

The following tokens are recognized as names of days of the week:

3 - Month names

The following tokens are recognized as names of months:

4 - Interval literal

A literal that represents a time span.

Syntax

[ @ ] [-] { quantity subtype-unit }[...] [ AGO ]

Parameters

@

Ignored

- (minus)

Specifies a negative interval value.

quantity

Integer numeric constant

subtype-unit

See Interval subtype units for valid values. Subtype units must be specified for year-month intervals; they are optional for day-time intervals.

AGO

Specifies a negative interval value. AGO and - (minus) are synonymous.

Notes

• The amounts of different units are implicitly added up with appropriate sign accounting.

• The boundaries of an interval constant are:

  • 9223372036854775807 usec to -9223372036854775807 usec

  • 296533 years 3 mons 21 days 04:00:54.775807 to -296533 years -3 mons -21 days -04:00:54.775807

• The range of an interval constant is +/– 263 – 1 microseconds.

• In Vertica, interval fields are additive and accept large floating-point numbers.

Examples

See Specifying interval input.

4.1 - Interval subtype units

The following tables lists subtype units that you can specify in an interval literal, divided into major categories:

• Year-month subtype units

• Day-time subtype units

Year-month subtype units

Day-time subtype units

Processing m input

Vertica uses context to interpret the input unit m as months or minutes. For example, the following command creates a one-column table with an interval value:

=> CREATE TABLE int_test(i INTERVAL YEAR TO MONTH);

Given the following INSERT statement, Vertica interprets the interval literal 1y 6m as 1 year 6 months:

=> INSERT INTO int_test VALUES('1y 6m');
 OUTPUT
--------
      1
(1 row)
=> COMMIT;
COMMIT
=> SET INTERVALSTYLE TO UNITS;
SET
=> SELECT * FROM int_test;
        i
-----------------
 1 year 6 months
(1 row)

The following ALTER TABLE statement adds a DAY TO MINUTE interval column to table int_test:

=>  ALTER TABLE int_test ADD COLUMN x INTERVAL DAY TO MINUTE;
ALTER TABLE

The next INSERT statement sets the first and second columns to 3y 20m and 1y 6m, respectively. In this case, Vertica interprets the m input literals in two ways:

• For column i, Vertica interprets the m input as months, and displays 4 years 8 months.

• For column x, Vertica interprets the m input as minutes. Because the interval is defined as DAY TO MINUTE, it converts the inserted input value 1y 6m to 365 days 6 minutes:

=> INSERT INTO int_test VALUES ('3y 20m', '1y 6m');
 OUTPUT
--------
      1
(1 row)

=> SELECT * FROM int_test;
        i         |        x
------------------+-----------------
 1 year 6 months  |
 4 years 8 months | 365 days 6 mins
(2 rows)

4.2 - Interval qualifier

Specifies how to interpret and format an interval literal for output, and optionally sets precision. Interval qualifiers are composed of one or two units:

unit [ TO unit ] [ (p) ]

where:

• unit specifies a day-time or year-month subtype.

• p specifies precision, an integer between 0 and 6.

  Note

  Precision only applies to SECOND units, specifying the number of decimal digits to show after the seconds value decimal point. The default precision for SECOND is 6.

  When SECOND is the second unit of a qualifier—for example, DAY TO SECOND or MINUTE TO SECOND—it has a precision of 2 places before the decimal point.

  For example:

  => SELECT INTERVAL '6 122.538987' MINUTE TO SECOND (5);
    ?column?
  -------------
   08:02.53899
  (1 row)
  

  For details, see Specifying interval precision.

If an interval omits an interval qualifier, the default is DAY TO SECOND(6).

Interval qualifiers are divided into two categories:

• day-time

• year-month

Day-time interval qualifiers

Year-month interval qualifiers

YEAR

Unconstrained

MONTH

Months within year

YEAR TO MONTH

Span of years and months

=> SELECT INTERVALYM '1 2';
 ?column?
----------
 1-2
(1 row)
=> SELECT INTERVAL '1 2' YEAR TO MONTH;
?column?
----------
1-2
(1 row)

Examples

See Controlling interval format.