Add information regarding date and time types and functions,
including arguments allowed.
This commit is contained in:
Thomas G. Lockhart
parent
54c38a95ee
commit
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@ -1,6 +1,6 @@
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.\" This is -*-nroff-*-
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.\" XXX standard disclaimer belongs here....
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.\" $Header: /cvsroot/pgsql/src/man/Attic/built-in.3,v 1.7 1997/05/16 07:13:46 thomas Exp $
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.\" $Header: /cvsroot/pgsql/src/man/Attic/built-in.3,v 1.8 1997/07/02 14:13:14 thomas Exp $
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.TH BUILT-INS INTRO 04/01/97 PostgreSQL PostgreSQL
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.SH "DESCRIPTION"
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This section describes the data types, functions and operators
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@ -82,7 +82,11 @@ several possibilities for formats, such as date and time types.
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Some date and time types share code for data input. For those types (currently
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.IR datetime
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and
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.IR abstime )
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.IR abstime
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, and
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.IR timespan
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and
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.IR reltime )
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the input can have any of a wide variety of styles. For numeric date representations,
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European and US conventions can differ, and the proper interpretation is obtained
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by using the
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@ -129,22 +133,22 @@ offsets to GMT (e.g. "-08" or "-08:00" when in Pacific Standard Time).
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Dates are stored internally in Greenwich Mean Time. Input and output routines
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translate time to the local time zone of the server.
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.PP
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All special values allowed for
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.IR "absolute time"
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are also allowed for
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.IR "datetime".
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The special values \*(lqcurrent\*(rq,
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\*(lqinfinity\*(rq and \*(lq-infinity\*(rq are provided.
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\*(lqinfinity\*(rq specifies a time later than any valid time, and
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\*(lq-infinity\*(rq specifies a time earlier than any valid time.
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\*(lqcurrent\*(rq indicates that the current time should be
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The special values `current',
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`infinity' and `-infinity' are provided.
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`infinity' specifies a time later than any valid time, and
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`-infinity' specifies a time earlier than any valid time.
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`current' indicates that the current time should be
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substituted whenever this value appears in a computation.
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.PP
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The strings \*(lqnow\*(rq and \*(lqepoch\*(rq can be used to specify
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time values. \*(lqnow\*(rq means the current time, and differs from
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\*(lqcurrent\*(rq in that the current time is immediately substituted
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for it. \*(lqepoch\*(rq means Jan 1 00:00:00 1970 GMT.
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The strings
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`now',
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`today',
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`yesterday',
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`tomorrow',
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and `epoch' can be used to specify
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time values. `now' means the current time, and differs from
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`current' in that the current time is immediately substituted
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for it. `epoch' means Jan 1 00:00:00 1970 GMT.
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.SH "TIMESPAN"
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General-use time span is input using a wide range of
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@ -165,10 +169,10 @@ Time span is specified with the following syntax:
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@ Quantity Unit [Direction]
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.sp
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where
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Quantity is ..., '-1', '0', `1', `2', ...
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Quantity is ..., `-1', `0', `1', `2', ...
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Unit is `second', `minute', `hour', `day', `week', `month', `year',
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or abbreviations or plurals of these units.
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Direction is ``ago''
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Direction is `ago'.
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.fi
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.SH "ABSOLUTE TIME"
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Absolute time (abstime) is a limited-range (+/- 68 years) and limited-precision (1 sec)
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@ -196,17 +200,10 @@ Valid dates are from Dec 13 20:45:53 1901 GMT to Jan 19 03:14:04
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using Greenwich Mean Time; the input and output routines default to
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the local time zone.
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.PP
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The special absolute time values \*(lqcurrent\*(rq,
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\*(lqinfinity\*(rq and \*(lq-infinity\*(rq are also provided.
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\*(lqinfinity\*(rq specifies a time later than any valid time, and
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\*(lq-infinity\*(rq specifies a time earlier than any valid time.
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\*(lqcurrent\*(rq indicates that the current time should be
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substituted whenever this value appears in a computation.
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.PP
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The strings \*(lqnow\*(rq and \*(lqepoch\*(rq can be used to specify
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time values. \*(lqnow\*(rq means the current time, and differs from
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\*(lqcurrent\*(rq in that the current time is immediately substituted
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for it. \*(lqepoch\*(rq means Jan 1 00:00:00 1970 GMT.
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All special values allowed for
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.IR "datetime"
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are also allowed for
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.IR "absolute time".
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.SH "RELATIVE TIME"
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Relative time (reltime) is a limited-range (+/- 68 years) and limited-precision (1 sec)
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@ -506,6 +503,16 @@ tinterval
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.SH "FUNCTIONS"
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Many data types have functions available for conversion to other related types.
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In addition, there are some type-specific functions.
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.PP
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For the
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date_part() and date_trunc()
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functions, arguments can be
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`year', `month', `day', `hour', `minute', and `second',
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as well as the more specialized quantities
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`decade', `century', `millenium', `millisecond', and `microsecond'.
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date_part() also allows
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`dow'
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to return day of week and `epoch' to return seconds since 1970.
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.nf
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Functions:
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@ -521,6 +528,7 @@ date
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datetime
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abstime abstime(datetime) convert to abstime
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float8 date_part(text,datetime) specified portion of date field
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datetime date_trunc(text,datetime) truncate date at specified units
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bool isfinite(datetime) TRUE if this is a finite time
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reltime
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@ -550,6 +558,7 @@ circle
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float8 diameter(circle) diameter of circle
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float8 area(circle) area of circle
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.fi
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.SH "BINARY OPERATORS"
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This list was generated from the Postgres system catalogs with the
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query:
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