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.\" This is -*-nroff-*-
.\" XXX standard disclaimer belongs here....
.\" $Header: /cvsroot/pgsql/src/man/Attic/pgbuiltin.3,v 1.11 1998/06/24 13:21:29 momjian Exp $
.TH PGBUILTIN INTRO 04/01/97 PostgreSQL PostgreSQL
.PP
.SH "DESCRIPTION"
This section describes the data types, functions and operators
available to users in Postgres as it is distributed.
.PP
.SH "PGBUILTIN TYPES"
Built-in types are installed in every database.
.IR "psql"
has a \ed command to show these types.
.PP
Users may add new types to Postgres using the
.IR "define type"
command described in this manual.
.PP
There are some data types defined by SQL/92 syntax which are mapped directly
into native Postgres types. Note that the "exact numerics"
.IR decimal
and
.IR numeric
have fully implemented syntax but currently (postgres v6.2) support only a limited
range of the values allowed by SQL/92.
.PP
.SH "List of SQL/92 types"
.PP
.if n .ta 2 +15 +25 +40
.if t .ta 0.5i +1.5i +3.0i
.in 0
.nf
\fBPOSTGRES Type\fP \fBSQL/92 Type\fP \fBMeaning\fP
char(n) character(n) fixed-length character string
varchar(n) character varying(n) variable-length character string
float4/8 float(p) floating-point number with precision p
float8 double precision double-precision floating-point number
float8 real double-precision floating-point number
int2 smallint signed two-byte integer
int4 int signed 4-byte integer
int4 integer signed 4-byte integer
int4 decimal(p,s) exact numeric for p <= 9, s = 0
int4 numeric(p,s) exact numeric for p == 9, s = 0
timestamp timestamp with time zone date/time
timespan interval general-use time span
.fi
.in
.PP
There are some constants and functions defined in SQL/92.
.PP
.SH "List of SQL/92 constants"
.PP
.if n .ta 2 +20 +40
.if t .ta 0.5i +1.5i +3.0i +4.0i
.in 0
.nf
\fBSQL/92 Function\fP \fBMeaning\fP
current_date date of current transaction
current_time time of current transaction
current_timestamp date and time of current transaction
.fi
.in
.PP
Many of the built-in types have obvious external formats. However, several
types are either unique to Postgres, such as open and closed paths, or have
several possibilities for formats, such as date and time types.
.PP
.SH "Syntax of date and time types"
Most date and time types share code for data input. For those types (
.IR datetime ,
.IR abstime ,
.IR timestamp ,
.IR timespan ,
.IR reltime ,
.IR date ,
and
.IR time )
the input can have any of a wide variety of styles. For numeric date representations,
European and US conventions can differ, and the proper interpretation is obtained
by using the
.IR set(l)
command before entering data.
Output formats can be set to one of three styles:
ISO-8601, SQL (traditional Oracle/Ingres), and traditional
Postgres (see section on
.IR "absolute time" )
with the SQL style having European and US variants (see
.IR set(l)).
In future releases, the number of date/time types will decrease, with the current
implementation of datetime becoming timestamp, timespan becoming interval,
and (possibly) abstime
and reltime being deprecated in favor of timestamp and interval.
.PP
.SH "DATETIME"
General-use date and time is input using a wide range of
styles, including ISO-compatible, SQL-compatible, traditional
Postgres (see section on
.IR "absolute time")
and other permutations of date and time. Output styles can be ISO-compatible,
SQL-compatible, or traditional Postgres, with the default set to be compatible
with Postgres v6.0.
.PP
datetime is specified using the following syntax:
.PP
.nf
Year-Month-Day [ Hour : Minute : Second ] [AD,BC] [ Timezone ]
.nf
YearMonthDay [ Hour : Minute : Second ] [AD,BC] [ Timezone ]
.nf
Month Day [ Hour : Minute : Second ] Year [AD,BC] [ Timezone ]
.sp
where
Year is 4013 BC, ..., very large
Month is Jan, Feb, ..., Dec or 1, 2, ..., 12
Day is 1, 2, ..., 31
Hour is 00, 02, ..., 23
Minute is 00, 01, ..., 59
Second is 00, 01, ..., 59 (60 for leap second)
Timezone is 3 characters or ISO offset to GMT
.fi
.PP
Valid dates are from Nov 13 00:00:00 4013 BC GMT to far into the future.
Timezones are either three characters (e.g. "GMT" or "PST") or ISO-compatible
offsets to GMT (e.g. "-08" or "-08:00" when in Pacific Standard Time).
Dates are stored internally in Greenwich Mean Time. Input and output routines
translate time to the local time zone of the server.
.PP
The special values `current',
`infinity' and `-infinity' are provided.
`infinity' specifies a time later than any valid time, and
`-infinity' specifies a time earlier than any valid time.
`current' indicates that the current time should be
substituted whenever this value appears in a computation.
.PP
The strings
`now',
`today',
`yesterday',
`tomorrow',
and `epoch' can be used to specify
time values. `now' means the current time, and differs from
`current' in that the current time is immediately substituted
for it. `epoch' means Jan 1 00:00:00 1970 GMT.
.PP
.SH "TIMESPAN"
General-use time span is input using a wide range of
syntaxes, including ISO-compatible, SQL-compatible, traditional
Postgres (see section on
.IR "relative time"
) and other permutations of time span. Output formats can be ISO-compatible,
SQL-compatible, or traditional Postgres, with the default set to be Postgres-compatible.
Months and years are a "qualitative" time interval, and are stored separately
from the other "quantitative" time intervals such as day or hour. For date arithmetic,
the qualitative time units are instantiated in the context of the relevant date or time.
.PP
Time span is specified with the following syntax:
.PP
.nf
Quantity Unit [Quantity Unit...] [Direction]
.nf
@ Quantity Unit [Direction]
.sp
where
Quantity is ..., `-1', `0', `1', `2', ...
Unit is `second', `minute', `hour', `day', `week', `month', `year',
or abbreviations or plurals of these units.
Direction is `ago'.
.fi
.PP
.SH "ABSOLUTE TIME"
Absolute time (abstime) is a limited-range (+/- 68 years) and limited-precision (1 sec)
date data type.
.IR "datetime"
may be preferred, since it
covers a larger range with greater precision.
.PP
Absolute time is specified using the following syntax:
.PP
.nf
Month Day [ Hour : Minute : Second ] Year [ Timezone ]
.sp
where
Month is Jan, Feb, ..., Dec
Day is 1, 2, ..., 31
Hour is 01, 02, ..., 24
Minute is 00, 01, ..., 59
Second is 00, 01, ..., 59
Year is 1901, 1902, ..., 2038
.fi
.PP
Valid dates are from Dec 13 20:45:53 1901 GMT to Jan 19 03:14:04
2038 GMT. As of Version 3.0, times are no longer read and written
using Greenwich Mean Time; the input and output routines default to
the local time zone.
.PP
All special values allowed for
.IR "datetime"
are also allowed for
.IR "absolute time".
.PP
.SH "RELATIVE TIME"
Relative time (reltime) is a limited-range (+/- 68 years) and limited-precision (1 sec)
time span data type.
.IR "timespan"
may be preferred, since it
covers a larger range with greater precision, allows multiple units
for an entry, and correctly handles qualitative time
units such as year and month. For reltime, only one quantity and unit is allowed
per entry, which can be inconvenient for complicated time spans.
.PP
Relative time is specified with the following syntax:
.PP
.nf
@ Quantity Unit [Direction]
.sp
where
Quantity is `1', `2', ...
Unit is ``second'', ``minute'', ``hour'', ``day'', ``week'',
``month'' (30-days), or ``year'' (365-days),
or PLURAL of these units.
Direction is ``ago''
.fi
.PP
.RB ( Note :
Valid relative times are less than or equal to 68 years.)
In addition, the special relative time \*(lqUndefined RelTime\*(rq is
provided.
.PP
.SH "TIMESTAMP"
This is currently a limited-range absolute time which closely resembles the
.IR abstime
data type. It shares the general input parser with the other date/time types.
In future releases this type will absorb the capabilities of the datetime type
and will move toward SQL92 compliance.
.PP
timestamp is specified using the same syntax as for datetime.
.PP
.SH "TIME RANGES"
Time ranges are specified as:
.PP
.nf
[ 'abstime' 'abstime']
.fi
where
.IR abstime
is a time in the absolute time format. Special abstime values such as
\*(lqcurrent\*(rq, \*(lqinfinity\*(rq and \*(lq-infinity\*(rq can be used.
.PP
.SH "Syntax of geometric types"
.SH "POINT"
Points are specified using the following syntax:
.PP
.nf
( x , y )
.nf
x , y
.sp
where
x is the x-axis coordinate as a floating point number
y is the y-axis coordinate as a floating point number
.fi
.PP
.SH "LSEG"
Line segments are represented by pairs of points.
.PP
lseg is specified using the following syntax:
.PP
.nf
( ( x1 , y1 ) , ( x2 , y2 ) )
.nf
( x1 , y1 ) , ( x2 , y2 )
.nf
x1 , y1 , x2 , y2
.sp
where
(x1,y1) and (x2,y2) are the endpoints of the segment
.fi
.PP
.SH "BOX"
Boxes are represented by pairs of points which are opposite
corners of the box.
.PP
box is specified using the following syntax:
.PP
.nf
( ( x1 , y1 ) , ( x2 , y2 ) )
.nf
( x1 , y1 ) , ( x2 , y2 )
.nf
x1 , y1 , x2 , y2
.sp
where
(x1,y1) and (x2,y2) are opposite corners
.fi
.PP
Boxes are output using the first syntax.
The corners are reordered on input to store
the lower left corner first and the upper right corner last.
Other corners of the box can be entered, but the lower
left and upper right corners are determined from the input and stored.
.PP
.SH "PATH"
Paths are represented by sets of points. Paths can be "open", where
the first and last points in the set are not connected, and "closed",
where the first and last point are connected. Functions
.IR popen(p)
and
.IR pclose(p)
are supplied to force a path to be open or closed, and functions
.IR isopen(p)
and
.IR isclosed(p)
are supplied to select either type in a query.
.PP
path is specified using the following syntax:
.PP
.nf
( ( x1 , y1 ) , ... , ( xn , yn ) )
.nf
[ ( x1 , y1 ) , ... , ( xn , yn ) ]
.nf
( x1 , y1 ) , ... , ( xn , yn )
.nf
( x1 , y1 , ... , xn , yn )
.nf
x1 , y1 , ... , xn , yn
.sp
where
(x1,y1),...,(xn,yn) are points 1 through n
a leading "[" indicates an open path
a leading "(" indicates a closed path
.fi
.PP
Paths are output using the first syntax.
Note that Postgres versions prior to
v6.1 used a format for paths which had a single leading parenthesis, a "closed" flag,
an integer count of the number of points, then the list of points followed by a
closing parenthesis. The built-in function upgradepath() is supplied to convert
paths dumped and reloaded from pre-v6.1 databases.
.PP
.SH "POLYGON"
Polygons are represented by sets of points. Polygons should probably be
considered
equivalent to closed paths, but are stored differently and have their own
set of support routines.
.PP
polygon is specified using the following syntax:
.PP
.nf
( ( x1 , y1 ) , ... , ( xn , yn ) )
.nf
( x1 , y1 ) , ... , ( xn , yn )
.nf
( x1 , y1 , ... , xn , yn )
.nf
x1 , y1 , ... , xn , yn
.sp
where
(x1,y1),...,(xn,yn) are points 1 through n
.fi
.PP
Polygons are output using the first syntax.
The last format is supplied to be backward compatible with v6.0 and earlier
path formats and will not be supported in future versions of Postgres.
a single leading "(" indicates a v6.0-compatible format
( x1 , ... , xn , y1 , ... , yn )
Note that Postgres versions prior to
v6.1 used a format for polygons which had a single leading parenthesis, the list
of x-axis coordinates, the list of y-axis coordinates, followed by a closing parenthesis.
The built-in function upgradepoly() is supplied to convert
polygons dumped and reloaded from pre-v6.1 databases.
.PP
.SH "CIRCLE"
Circles are represented by a center point and a radius.
.PP
circle is specified using the following syntax:
.PP
.nf
< ( x , y ) , r >
.nf
( ( x , y ) , r )
.nf
( x , y ) , r
.nf
x , y , r
.sp
where
(x,y) is the center of the circle
r is the radius of the circle
.fi
.PP
Circles are output using the first syntax.
.PP
.SH "Built-in operators and functions"
.SH OPERATORS
Postgres provides a large number of built-in operators on system types.
These operators are declared in the system catalog
\*(lqpg_operator\*(rq. Every entry in \*(lqpg_operator\*(rq includes
the object ID of the procedure that implements the operator.
.PP
Users may invoke operators using the operator name, as in:
.PP
.in 1i
.nf
select * from emp where salary < 40000;
.fi
.in
.PP
Alternatively, users may call the functions that implement the
operators directly. In this case, the query above would be expressed
as:
.PP
.in 1i
.nf
select * from emp where int4lt(salary, 40000);
.fi
.in
.PP
.IR "psql"
has a \ed command to show these operators.
.PP
.SH "FUNCTIONS"
Many data types have functions available for conversion to other related types.
In addition, there are some type-specific functions. Functions which are also
available through operators are documented as operators only.
.PP
Some functions defined for text are also available for char() and varchar().
.PP
For the
date_part() and date_trunc()
functions, arguments can be
`year', `month', `day', `hour', `minute', and `second',
as well as the more specialized quantities
`decade', `century', `millenium', `millisecond', and `microsecond'.
date_part() allows `dow'
to return day of week and `epoch' to return seconds since 1970 for datetime
and 'epoch' to return total elapsed seconds for timespan.
.nf
Functions:
integer
float8 float(int) convert integer to floating point
float4 float4(int) convert integer to floating point
float
int integer(float) convert floating point to integer
text
text lower(text) convert text to lower case
text lpad(text,int,text) left pad string to specified length
text ltrim(text,text) left trim characters from text
text position(text,text) extract specified substring
text rpad(text,int,text) right pad string to specified length
text rtrim(text,text) right trim characters from text
text substr(text,int[,int]) extract specified substring
text upper(text) convert text to upper case
abstime
bool isfinite(abstime) TRUE if this is a finite time
datetime datetime(abstime) convert to datetime
date
datetime datetime(date) convert to datetime
datetime datetime(date,time) convert to datetime
datetime
timespan age(datetime,datetime) date difference preserving months and years
float8 date_part(text,datetime) specified portion of date field
datetime date_trunc(text,datetime) truncate date at specified units
bool isfinite(datetime) TRUE if this is a finite time
abstime abstime(datetime) convert to abstime
reltime
timespan timespan(reltime) convert to timespan
time
datetime datetime(date,time) convert to datetime
timespan
float8 date_part(text,timespan) specified portion of time field
bool isfinite(timespan) TRUE if this is a finite time
reltime reltime(timespan) convert to reltime
box
box box(point,point) convert points to box
float8 area(box) area of box
path
bool isopen(path) TRUE if this is an open path
bool isclosed(path) TRUE if this is a closed path
circle
circle circle(point,float8) convert to circle
polygon polygon(npts,circle) convert to polygon with npts points
float8 center(circle) radius of circle
float8 radius(circle) radius of circle
float8 diameter(circle) diameter of circle
float8 area(circle) area of circle
.fi
.PP
SQL/92 defines functions with specific syntax. Some of these
are implemented using other Postgres functions.
.nf
SQL/92 Functions:
text
text position(text in text) extract specified substring
text substring(text [from int] [for int])
extract specified substring
text trim([leading|trailing|both] [text] from text)
trim characters from text
.fi
.PP
.SH "ADDITIONAL INFORMATION"
.IR "psql"
has a variety of \ed commands for showing system information.
Consult those
.IR "psql"
commands for more listings.
.PP
.SH "SEE ALSO"
.IR set(l),
.IR show(l),
.IR reset(l),
.IR psql(1).
For examples on specifying literals of built-in types, see
.IR SQL(l).
.PP
.SH BUGS
Although most of the input and output functions corresponding to the
base types (e.g., integers and floating point numbers) do some
error-checking, some are not particularly rigorous about it. More
importantly, few of the operators and functions (e.g.,
addition and multiplication) perform any error-checking at all.
Consequently, many of the numeric operators can (for example)
silently underflow or overflow.
.PP
Some of the input and output functions are not invertible. That is,
the result of an output function may lose precision when compared to
the original input.
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