data types types data types Postgres has a rich set of native data types available to users. Users may add new types to Postgres using the CREATE TYPE command. shows all general-purpose data types available to users. Most of the alternative names listed in the Aliases column are the names used internally by Postgres for historical reasons. In addition, some internally used or deprecated types are available, but they are not documented here. 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 the date and time types. Type Name Aliases Description bigint int8 signed eight-byte integer bit fixed-length bit string bit varying(n) varbit(n) variable-length bit string boolean bool logical Boolean (true/false) box rectangular box in 2D plane character(n) char(n) fixed-length character string character varying(n) varchar(n) variable-length character string cidr IP network address circle circle in 2D plane date calendar date (year, month, day) double precision float8 double precision floating-point number inet IP host address integer int, int4 signed four-byte integer interval general-use time span line infinite line in 2D plane lseg line segment in 2D plane macaddr MAC address money US-style currency numeric(p, s) decimal(p, s) exact numeric with selectable precision oid object identifier path open and closed geometric path in 2D plane point geometric point in 2D plane polygon closed geometric path in 2D plane real float4 single precision floating-point number smallint int2 signed two-byte integer serial autoincrementing four-byte integer text variable-length character string time [ without time zone ] time of day time with time zone time of day, including time zone timestamp [ with time zone ] date and time The following types (or spellings thereof) are specified by SQL: bit, bit varying, boolean, char, character, character varying, varchar, date, double precision, integer, interval, numeric, decimal, real, smallint, time, timestamp (both with or without time zone). Most of the input and output functions corresponding to the base types (e.g., integers and floating point numbers) do some error-checking. Some of the operators and functions (e.g., addition and multiplication) do not perform run-time error-checking in the interests of improving execution speed. On some systems, for example, the numeric operators for some data types may silently underflow or overflow. 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. data types numeric integer smallint bigint int4 integer int2 smallint int8 bigint numeric (data type) decimal numeric real double precision float4 real float8 double precision floating point Numeric types consist of two-, four-, and eight-byte integers, four- and eight-byte floating point numbers and fixed-precision decimals. Type Name Storage Description Range smallint 2 bytes Fixed-precision -32768 to +32767 integer 4 bytes Usual choice for fixed-precision -2147483648 to +2147483647 bigint 8 bytes Very large range fixed-precision about 18 decimal places decimal variable User-specified precision no limit numeric variable User-specified precision no limit real 4 bytes Variable-precision 6 decimal places double precision 8 bytes Variable-precision 15 decimal places serial 4 bytes Identifier or cross-reference 0 to +2147483647 The syntax of constants for the numeric types is described in . The numeric types have a full set of corresponding arithmetic operators and functions. Refer to for more information. The bigint type may not be available on all platforms since it relies on compiler support for eight-byte integers. serial auto-increment serial sequences and serial type The serial type is a special-case type constructed by Postgres from other existing components. It is typically used to create unique identifiers for table entries. In the current implementation, specifying CREATE TABLE tablename (colname SERIAL); is equivalent to specifying: CREATE SEQUENCE tablename_colname_seq; CREATE TABLE tablename (colname integer DEFAULT nextval('tablename_colname_seq'); CREATE UNIQUE INDEX tablename_colname_key on tablename (colname); The implicit sequence created for the serial type will not be automatically removed when the table is dropped. Implicit sequences supporting the serial are not automatically dropped when a table containing a serial type is dropped. So, the following commands executed in order will likely fail: CREATE TABLE tablename (colname SERIAL); DROP TABLE tablename; CREATE TABLE tablename (colname SERIAL); The sequence will remain in the database until explicitly dropped using DROP SEQUENCE. The money type is deprecated. Use numeric or decimal instead, in combination with the to_char function. The money type may become a locale-aware layer over the numeric type in a future release. The money type stores U.S.-style currency with fixed decimal point representation. If Postgres is compiled with locale support then the money type uses locale-specific output formatting. Input is accepted in a variety of formats, including integer and floating point literals, as well as typical currency formatting, such as '$1,000.00'. Output is in the latter form. Type Name Storage Description Range money 4 bytes Fixed-precision -21474836.48 to +21474836.47 character strings data types strings character strings text character strings Type name Description character(n), char(n) Fixed-length blank padded character varying(n), varchar(n) Variable-length with limit text Variable unlimited length SQL defines two primary character types: character(n) and character varying(n), where n is a positive integer. Both of these types can store strings up to n characters in length. An attempt to store a longer string into a column of these types will result in an error, unless the excess characters are all spaces, in which case the string will be truncated to the maximum length. (This somewhat bizarre exception is required by the SQL standard.) If the string to be stored is shorter than the declared length, values of type character will be space-padded; values of type character varying will simply store the shorter string. Prior to PostgreSQL 7.2, strings that were too long were silently truncated, no error was raised. The notations char(n) and varchar(n) are aliases for character(n) and character varying(n), respectively. character without length specifier is equivalent to character(1); if character varying is used without length specifier, the type accepts strings of any size. The latter is a PostgreSQL extension. In addition, PostgreSQL supports the more general text type, which stores strings of any length. Unlike character varying, text does not require an explicit declared upper limit on the size of the string. Although the type text is not in the SQL standard, many other RDBMS packages have it as well. The storage requirement for data of these types is 4 bytes plus the actual string, and in case of character plus the padding. Long strings will actually be compressed by the system automatically. In any case, the longest possible character string that can be stored is about 1 GB. (The maximum value that will be allowed for n in the data type declaration is actually larger than that. It wouldn't be very useful to change this because with multi-byte character encodings the number of characters and bytes can be quite different anyway.) There are no performance differences between these three types, apart from the increased storage size when using the blank-padded type. Refer to for information about the syntax of string literals, and to for information about available operators and functions. CREATE TABLE test1 (a character(4)); INSERT INTO test1 VALUES ('ok'); SELECT a, char_length(a) FROM test1; -- a | char_length ------+------------- ok | 4 CREATE TABLE test2 (b varchar(5)); INSERT INTO test2 VALUES ('ok'); INSERT INTO test2 VALUES ('good '); INSERT INTO test2 VALUES ('too long'); ERROR: value too long for type character varying(5) SELECT b, char_length(b) FROM test2; b | char_length -------+------------- ok | 2 good | 5 The char_length function is discussed in . There are two other fixed-length character types in Postgres. The name type exists only for storage of internal catalog names and is not intended for use by the general user. Its length is currently defined as 32 bytes (31 characters plus terminator) but should be referenced using the macro NAMEDATALEN. The length is set at compile time (and is therefore adjustable for special uses); the default maximum length may change in a future release. The type "char" (note the quotes) is different from char(1) in that it only uses one byte of storage. It is internally used in the system catalogs as a poor-man's enumeration type. Type Name Storage Description "char" 1 byte Single character internal type name 32 bytes Thirty-one character internal type Postgres supports the full set of SQL date and time types. Type Description Storage Earliest Latest Resolution timestamp both date and time 8 bytes 4713 BC AD 1465001 1 microsecond / 14 digits timestamp [ with time zone ] date and time with time zone 8 bytes 1903 AD 2037 AD 1 microsecond / 14 digits interval for time intervals 12 bytes -178000000 years 178000000 years 1 microsecond date dates only 4 bytes 4713 BC 32767 AD 1 day time [ without time zone ] times of day only 4 bytes 00:00:00.00 23:59:59.99 1 microsecond time with time zone times of day only 4 bytes 00:00:00.00+12 23:59:59.99-12 1 microsecond To ensure compatibility to earlier versions of Postgres we also continue to provide datetime (equivalent to timestamp) and timespan (equivalent to interval), however support for these is now restricted to having an implicit translation to timestamp and interval. The types abstime and reltime are lower precision types which are used internally. You are discouraged from using any of these types in new applications and are encouraged to move any old ones over when appropriate. Any or all of these internal types might disappear in a future release. Date and time input is accepted in almost any reasonable format, including ISO-8601, SQL-compatible, traditional Postgres, and others. The ordering of month and day in date input can be ambiguous, therefore a setting exists to specify how it should be interpreted in ambiguous cases. The command SET DateStyle TO 'US' or SET DateStyle TO 'NonEuropean' specifies the variant "month before day", the command SET DateStyle TO 'European' sets the variant "day before month". The ISO style is the default but this default can be changed at compile time or at run time. See for the exact parsing rules of date/time input and for the recognized time zones. Remember that any date or time input needs to be enclosed into single quotes, like text strings. Refer to for more information. SQL requires the following syntax type 'value' but Postgres is more flexible. date data type The following are possible inputs for the date type. Example Description January 8, 1999 Unambiguous 1999-01-08 ISO-8601 format, preferred 1/8/1999 US; read as August 1 in European mode 8/1/1999 European; read as August 1 in US mode 1/18/1999 US; read as January 18 in any mode 19990108 ISO-8601 year, month, day 990108 ISO-8601 year, month, day 1999.008 Year and day of year 99008 Year and day of year January 8, 99 BC Year 99 before the Common Era Month Abbreviations April Apr August Aug December Dec February Feb January Jan July Jul June Jun March Mar November Nov October Oct September Sep, Sept The month May has no explicit abbreviation, for obvious reasons. Day Abbreviation Sunday Sun Monday Mon Tuesday Tue, Tues Wednesday Wed, Weds Thursday Thu, Thur, Thurs Friday Fri Saturday Sat time data type Per SQL99, this type can be referenced as time and as time without time zone. The following are valid time inputs. Example Description 04:05:06.789 ISO-8601 04:05:06 ISO-8601 04:05 ISO-8601 040506 ISO-8601 04:05 AM Same as 04:05; AM does not affect value 04:05 PM Same as 16:05; input hour must be <= 12 z Same as 00:00:00 zulu Same as 00:00:00 allballs Same as 00:00:00 This type is defined by SQL92, but the definition exhibits fundamental deficiencies that render the type nearly useless. In most cases, a combination of date, time, and timestamp should provide a complete range of date/time functionality required by any application. time with time zone accepts all input also legal for the time type, appended with a legal time zone, as follows: Example Description 04:05:06.789-8 ISO-8601 04:05:06-08:00 ISO-8601 04:05-08:00 ISO-8601 040506-08 ISO-8601 Refer to for more examples of time zones. timestamp data type Valid input for the timestamp type consists of a concatenation of a date and a time, followed by an optional AD or BC, followed by an optional time zone. (See below.) Thus 1999-01-08 04:05:06 -8:00 is a valid timestamp value that is ISO-compliant. In addition, the wide-spread format January 8 04:05:06 1999 PST is supported. Time Zone Description PST Pacific Standard Time -8:00 ISO-8601 offset for PST -800 ISO-8601 offset for PST -8 ISO-8601 offset for PST interval intervals can be specified with the following syntax: Quantity Unit [Quantity Unit...] [Direction] @ Quantity Unit [Direction] where: Quantity is ..., -1, 0, 1, 2, ...; Unit is second, minute, hour, day, week, month, year, decade, century, millennium, or abbreviations or plurals of these units; Direction can be ago or empty. time current date current The following SQL-compatible functions can be used as date or time input for the corresponding data type: CURRENT_DATE, CURRENT_TIME, CURRENT_TIMESTAMP. Postgres also supports several special constants for convenience. Constant Description current Current transaction time, deferred epoch 1970-01-01 00:00:00+00 (Unix system time zero) infinity Later than other valid times -infinity Earlier than other valid times invalid Illegal entry now Current transaction time today Midnight today tomorrow Midnight tomorrow yesterday Midnight yesterday 'now' is resolved when the value is inserted, 'current' is resolved every time the value is retrieved. So you probably want to use 'now' in most applications. (Of course you really want to use CURRENT_TIMESTAMP, which is equivalent to 'now'.) date output format Formatting time output format Formatting Output formats can be set to one of the four styles ISO-8601, SQL (Ingres), traditional Postgres, and German, using the SET DateStyle. The default is the ISO format. Style Specification Description Example 'ISO' ISO-8601 standard 1997-12-17 07:37:16-08 'SQL' Traditional style 12/17/1997 07:37:16.00 PST 'Postgres' Original style Wed Dec 17 07:37:16 1997 PST 'German' Regional style 17.12.1997 07:37:16.00 PST The output of the date and time styles is of course only the date or time part in accordance with the above examples. The SQL style has European and non-European (US) variants, which determines whether month follows day or vice versa. (See also above at Date/Time Input, how this setting affects interpretation of input values.) Style Specification Description Example European day/month/year 17/12/1997 15:37:16.00 MET US month/day/year 12/17/1997 07:37:16.00 PST interval output looks like the input format, except that units like week or century are converted to years and days. In ISO mode the output looks like [ Quantity Units [ ... ] ] [ Days ] Hours:Minutes [ ago ] There are several ways to affect the appearance of date/time types: The PGDATESTYLE environment variable used by the backend directly on postmaster start-up. The PGDATESTYLE environment variable used by the frontend libpq on session start-up. SET DATESTYLE SQL command. time zones Postgres endeavors to be compatible with SQL92 definitions for typical usage. However, the SQL92 standard has an odd mix of date and time types and capabilities. Two obvious problems are: Although the date type does not have an associated time zone, the time type can or does. Time zones in the real world can have no meaning unless associated with a date as well as a time since the offset may vary through the year with daylight savings time boundaries. The default time zone is specified as a constant integer offset from GMT/UTC. It is not possible to adapt to daylight savings time when doing date/time arithmetic across DST boundaries. To address these difficulties, we recommend using date/time types that contain both date and time when using time zones. We recommend not using the SQL92 type TIME WITH TIME ZONE (though it is supported by Postgres for legacy applications and for compatibility with other RDBMS implementations). Postgres assumes local time for any type containing only date or time. Further, time zone support is derived from the underlying operating system time zone capabilities, and hence can handle daylight savings time and other expected behavior. Postgres obtains time zone support from the underlying operating system for dates between 1902 and 2038 (near the typical date limits for Unix-style systems). Outside of this range, all dates are assumed to be specified and used in Universal Coordinated Time (UTC). All dates and times are stored internally in UTC, traditionally known as Greenwich Mean Time (GMT). Times are converted to local time on the database server before being sent to the client frontend, hence by default are in the server time zone. There are several ways to affect the time zone behavior: The TZ environment variable is used by the backend directly on postmaster start-up as the default time zone. The PGTZ environment variable, if set at the client, is used by libpq to send a SET TIME ZONE command to the backend upon connection. The SQL command SET TIME ZONE sets the time zone for the session. The SQL92 qualifier on timestamp AT TIME ZONE 'zone' where zone can be specified as a text time zone (e.g. 'PST') or as an interval (e.g. INTERVAL '-08:00'). If an invalid time zone is specified, the time zone becomes GMT (on most systems anyway). If the runtime option AUSTRALIAN_TIMEZONES is set then CST and EST refer to Australian timezones, not American ones. Postgres uses Julian dates for all date/time calculations. They have the nice property of correctly predicting/calculating any date more recent than 4713BC to far into the future, using the assumption that the length of the year is 365.2425 days. Date conventions before the 19th century make for interesting reading, but are not consistent enough to warrant coding into a date/time handler. Boolean data type true false Postgres provides the SQL99 type boolean. boolean can have one of only two states: true or false. A third state, unknown, is represented by the SQL NULL state. Valid literal values for the true state are: TRUE 't' 'true' 'y' 'yes' '1' For the false state, the following values can be used: FALSE 'f' 'false' 'n' 'no' '0' Using the key words TRUE and FALSE is preferred (and SQL-compliant). CREATE TABLE test1 (a boolean, b text); INSERT INTO test1 VALUES (TRUE, 'sic est'); INSERT INTO test1 VALUES (FALSE, 'non est'); SELECT * FROM test1; a | b ---+--------- t | sic est f | non est SELECT * FROM test1 WHERE a; a | b ---+--------- t | sic est shows that boolean values are output using the letters t and f. Values of the boolean type cannot be cast directly to other types (e.g., CAST (boolval AS integer) does not work). This can be accomplished using the CASE expression: CASE WHEN boolval THEN 'value if true' ELSE 'value if false' END. See also . boolean uses 1 byte of storage. Geometric types represent two-dimensional spatial objects. The most fundamental type, the point, forms the basis for all of the other types. Geometric Type Storage Representation Description point 16 bytes (x,y) Point in space line 32 bytes ((x1,y1),(x2,y2)) Infinite line lseg 32 bytes ((x1,y1),(x2,y2)) Finite line segment box 32 bytes ((x1,y1),(x2,y2)) Rectangular box path 4+32n bytes ((x1,y1),...) Closed path (similar to polygon) path 4+32n bytes [(x1,y1),...] Open path polygon 4+32n bytes ((x1,y1),...) Polygon (similar to closed path) circle 24 bytes <(x,y),r> Circle (center and radius) A rich set of functions and operators is available to perform various geometric operations such as scaling, translation, rotation, and determining intersections. point Points are the fundamental two-dimensional building block for geometric types. point is specified using the following syntax: ( x , y ) x , y where the arguments are x The x-axis coordinate as a floating point number. y The y-axis coordinate as a floating point number. line Line segments (lseg) are represented by pairs of points. lseg is specified using the following syntax: ( ( x1 , y1 ) , ( x2 , y2 ) ) ( x1 , y1 ) , ( x2 , y2 ) x1 , y1 , x2 , y2 where the arguments are (x1,y1) (x2,y2) The end points of the line segment. box (data type) Boxes are represented by pairs of points that are opposite corners of the box. box is specified using the following syntax: ( ( x1 , y1 ) , ( x2 , y2 ) ) ( x1 , y1 ) , ( x2 , y2 ) x1 , y1 , x2 , y2 where the arguments are (x1,y1) (x2,y2) Opposite corners of the box. Boxes are output using the first syntax. The corners are reordered on input to store the upper right corner, then the lower left corner. Other corners of the box can be entered, but the lower left and upper right corners are determined from the input and stored. path (data type) Paths are represented by connected 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 popen(p) and pclose(p) are supplied to force a path to be open or closed, and functions isopen(p) and isclosed(p) are supplied to test for either type in a query. path is specified using the following syntax: ( ( x1 , y1 ) , ... , ( xn , yn ) ) [ ( x1 , y1 ) , ... , ( xn , yn ) ] ( x1 , y1 ) , ... , ( xn , yn ) ( x1 , y1 , ... , xn , yn ) x1 , y1 , ... , xn , yn where the arguments are (x,y) End points of the line segments comprising the path. A leading square bracket ("[") indicates an open path, while a leading parenthesis ("(") indicates a closed path. Paths are output using the first syntax. 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. polygon is specified using the following syntax: ( ( x1 , y1 ) , ... , ( xn , yn ) ) ( x1 , y1 ) , ... , ( xn , yn ) ( x1 , y1 , ... , xn , yn ) x1 , y1 , ... , xn , yn where the arguments are (x,y) End points of the line segments comprising the boundary of the polygon. Polygons are output using the first syntax. circle Circles are represented by a center point and a radius. circle is specified using the following syntax: < ( x , y ) , r > ( ( x , y ) , r ) ( x , y ) , r x , y , r where the arguments are (x,y) Center of the circle. r Radius of the circle. Circles are output using the first syntax. network addresses Postgres offers data types to store IP and MAC addresses. It is preferable to use these types over plain text types, because these types offer input error checking and several specialized operators and functions. Name Storage Description Range cidr 12 bytes IP networks valid IPv4 networks inet 12 bytes IP hosts and networks valid IPv4 hosts or networks macaddr 6 bytes MAC addresses customary formats IP v6 is not supported, yet. inet (data type) The inet type holds an IP host address, and optionally the identity of the subnet it is in, all in one field. The subnet identity is represented by the number of bits in the network part of the address (the netmask). If the netmask is 32, then the value does not indicate a subnet, only a single host. Note that if you want to accept networks only, you should use the cidr type rather than inet. The input format for this type is x.x.x.x/y where x.x.x.x is an IP address and y is the number of bits in the netmask. If the /y part is left off, then the netmask is 32, and the value represents just a single host. On display, the /y portion is suppressed if the netmask is 32. cidr The cidr type holds an IP network specification. Input and output formats follow Classless Internet Domain Routing conventions. The format for specifying classless networks is x.x.x.x/y where x.x.x.x is the network and y is the number of bits in the netmask. If y is omitted, it is calculated using assumptions from the older classful numbering system, except that it will be at least large enough to include all of the octets written in the input. Here are some examples: CIDR Input CIDR Displayed abbrev(CIDR) 192.168.100.128/25 192.168.100.128/25 192.168.100.128/25 192.168/24 192.168.0.0/24 192.168.0/24 192.168/25 192.168.0.0/25 192.168.0.0/25 192.168.1 192.168.1.0/24 192.168.1/24 192.168 192.168.0.0/24 192.168.0/24 128.1 128.1.0.0/16 128.1/16 128 128.0.0.0/16 128.0/16 128.1.2 128.1.2.0/24 128.1.2/24 10.1.2 10.1.2.0/24 10.1.2/24 10.1 10.1.0.0/16 10.1/16 10 10.0.0.0/8 10/8 The essential difference between inet and cidr data types is that inet accepts values with nonzero bits to the right of the netmask, whereas cidr does not. If you do not like the output format for inet or cidr values, try the host(), text(), and abbrev() functions. bit strings data type Bit strings are strings of 1's and 0's. They can be used to store or visualize bit masks. There are two SQL bit types: BIT(x) and BIT VARYING(x); where x is a positive integer. BIT type data must match the length x exactly; it is an error to attempt to store shorter or longer bit strings. BIT VARYING is of variable length up to the maximum length x; longer strings will be rejected. BIT without length is equivalent to BIT(1), BIT VARYING without length specification means unlimited length. Prior to PostgreSQL 7.2, BIT type data was zero-padded on the right. This was changed to comply with the SQL standard. To implement zero-padded bit strings, a combination of the concatenation operator and the substring function can be used. Refer to for information about the syntax of bit string constants. Bit-logical operators and string manipulation functions are available; see . CREATE TABLE test (a BIT(3), b BIT VARYING(5)); INSERT INTO test VALUES (B'101', B'00'); INSERT INTO test VALUES (B'10', B'101'); ERROR: bit string length does not match type bit(3) SELECT SUBSTRING(b FROM 1 FOR 2) FROM test;