<!--
-$Header: /cvsroot/pgsql/doc/src/sgml/datatype.sgml,v 1.49 2001/02/10 18:02:35 petere Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/datatype.sgml,v 1.50 2001/02/14 19:37:26 petere Exp $
-->
<chapter id="datatype">
<para>
<table id="datatype-table">
- <title><productname>Postgres</productname> Data Types</title>
- <titleabbrev>Data Types</titleabbrev>
+ <title>Data Types</title>
<tgroup cols="3">
<thead>
<row>
<row>
<entry><type>boolean</type></entry>
<entry><type>bool</type></entry>
- <entry>logical boolean (true/false)</entry>
+ <entry>logical Boolean (true/false)</entry>
</row>
<row>
<para>
<table tocentry="1">
- <title><productname>Postgres</productname> Numeric Types</title>
- <titleabbrev>Numerics</titleabbrev>
+ <title>Numeric Types</title>
<tgroup cols="4">
<thead>
<row>
- <entry>Numeric Type</entry>
+ <entry>Type Name</entry>
<entry>Storage</entry>
<entry>Description</entry>
<entry>Range</entry>
<row>
<entry>serial</entry>
<entry>4 bytes</entry>
- <entry>Identifer or cross-reference</entry>
+ <entry>Identifier or cross-reference</entry>
<entry>0 to +2147483647</entry>
</row>
</tbody>
<para>
<table tocentry="1">
- <title><productname>Postgres</productname> Monetary Types</title>
- <titleabbrev>Money</titleabbrev>
+ <title>Monetary Types</title>
<tgroup cols="4">
<thead>
<row>
- <entry>Monetary Type</entry>
+ <entry>Type Name</entry>
<entry>Storage</entry>
<entry>Description</entry>
<entry>Range</entry>
<para>
<table tocentry="1">
- <title><productname>Postgres</productname> Character Types</title>
- <titleabbrev>Characters</titleabbrev>
+ <title>Character Types</title>
<tgroup cols="4">
<thead>
<row>
- <entry>Character Type</entry>
+ <entry>Type Name</entry>
<entry>Storage</entry>
<entry>Recommendation</entry>
<entry>Description</entry>
<para>
<table tocentry="1">
- <title><productname>Postgres</productname> Specialty Character Type</title>
- <titleabbrev>Specialty Characters</titleabbrev>
+ <title>Specialty Character Type</title>
<tgroup cols="3">
<thead>
<row>
- <entry>Character Type</entry>
+ <entry>Type Name</entry>
<entry>Storage</entry>
<entry>Description</entry>
</row>
<para>
<table tocentry="1">
- <title><productname>Postgres</productname> Date/Time Types</title>
- <titleabbrev>Date/Time</titleabbrev>
+ <title>Date/Time Types</title>
<tgroup cols="4">
<thead>
<row>
<entry>8 bytes</entry>
<entry>4713 BC</entry>
<entry>AD 1465001</entry>
- <entry>1 microsec / 14 digits</entry>
+ <entry>1 microsecond / 14 digits</entry>
</row>
<row>
<entry><type>timestamp [ with time zone ]</type></entry>
<entry>8 bytes</entry>
<entry>1903 AD</entry>
<entry>2037 AD</entry>
- <entry>1 microsec / 14 digits</entry>
+ <entry>1 microsecond / 14 digits</entry>
</row>
<row>
<entry><type>interval</type></entry>
The following are possible inputs for the <type>date</type> type.
<table tocentry="1">
- <title><productname>Postgres</productname> Date Input</title>
- <titleabbrev>Date Inputs</titleabbrev>
+ <title>Date Input</title>
<tgroup cols="2">
<thead>
<row>
<para>
<table tocentry="1">
- <title><productname>Postgres</productname> Month Abbreviations</title>
- <titleabbrev>Month Abbreviations</titleabbrev>
+ <title>Month Abbreviations</title>
<tgroup cols="2">
<thead>
<row>
<para>
<table tocentry="1">
- <title><productname>Postgres</productname> Day of Week Abbreviations</title>
- <titleabbrev>Day of Week Abbreviations</titleabbrev>
+ <title>Day of the Week Abbreviations</title>
<tgroup cols="2">
<thead>
<row>
The following are valid <type>time</type> inputs.
<table tocentry="1">
- <title><productname>Postgres</productname> Time Input</title>
- <titleabbrev>Time Inputs</titleabbrev>
+ <title>Time Input</title>
<tgroup cols="2">
<thead>
<row>
as follows:
<table tocentry="1">
- <title><productname>Postgres</productname> Time With Time
- Zone Input</title>
- <titleabbrev>Time With Time Zone Inputs</titleabbrev>
+ <title>Time With Time Zone Input</title>
<tgroup cols="2">
<thead>
<row>
<para>
<table tocentry="1" id="datatype-timezone-table">
- <title><productname>Postgres</productname> Time Zone Input</title>
- <titleabbrev>Time Zone Inputs</titleabbrev>
+ <title>Time Zone Input</title>
<tgroup cols="2">
<thead>
<row>
<para>
The following <acronym>SQL</acronym>-compatible functions can be used as date or time
- input for the corresponding datatype: <literal>CURRENT_DATE</literal>,
+ input for the corresponding data type: <literal>CURRENT_DATE</literal>,
<literal>CURRENT_TIME</literal>, <literal>CURRENT_TIMESTAMP</literal>.
</para>
<para>
convenience.
<table tocentry="1">
- <title><productname>Postgres</productname> Special Date/Time Constants</title>
- <titleabbrev>Constants</titleabbrev>
+ <title>Special Date/Time Constants</title>
<tgroup cols="2">
<thead>
<row>
</tgroup>
</table>
<literal>'now'</literal> is resolved when the value is inserted, <literal>'current'</literal>
- is resolved everytime the value is retrieved. So you probably want to use <literal>'now'</literal>
+ is resolved every time the value is retrieved. So you probably want to use <literal>'now'</literal>
in most applications. (Of course you <emphasis>really</emphasis> want to use
<literal>CURRENT_TIMESTAMP</literal>, which is equivalent to <literal>'now'</literal>.)
</para>
The default is the <acronym>ISO</acronym> format.
<table tocentry="1">
- <title><productname>Postgres</productname> Date/Time Output Styles</title>
- <titleabbrev>Styles</titleabbrev>
+ <title>Date/Time Output Styles</title>
<tgroup cols="3">
<thead>
<row>
<para>
The <acronym>SQL</acronym> style has European and non-European (US) variants,
- which determines whether month follows day or vica versa. (See also above
+ which determines whether month follows day or vice versa. (See also above
at Date/Time Input, how this setting affects interpretation of input values.)
<table tocentry="1">
- <title><productname>Postgres</productname> Date Order Conventions</title>
- <titleabbrev>Date Order</titleabbrev>
+ <title>Date Order Conventions</title>
<tgroup cols="3">
<thead>
<row>
<note>
<para>
If the compiler option USE_AUSTRALIAN_RULES is set
- then <literal>EST</literal> refers to Australia Eastern Std Time,
+ then <literal>EST</literal> refers to Australia Eastern Standard Time,
which has an offset of +10:00 hours from UTC.
</para>
</note>
<para>
Date conventions before the 19th century make for interesting reading,
- but are not consistant enough to warrant coding into a date/time handler.
+ but are not consistent enough to warrant coding into a date/time handler.
</para>
</sect2>
<title>Boolean Type</title>
<para>
- <productname>Postgres</productname> supports the
- <acronym>SQL99</acronym> <type>boolean</type> type.
- <type>boolean</type> can have one of only two states: 'true' or
- 'false'. A third state, 'unknown', is represented by the SQL NULL
- state. <type>boolean</type> can be used in any boolean expression,
- and boolean expressions always evaluate to a result compatible
- with this type.
+ <productname>Postgres</productname> provides the
+ <acronym>SQL99</acronym> type <type>boolean</type>.
+ <type>boolean</type> can have one of only two states:
+ <quote>true</quote> or <quote>false</quote>. A third state,
+ <quote>unknown</quote>, is represented by the
+ <acronym>SQL</acronym> NULL state.
</para>
<para>
- <type>boolean</type> uses 1 byte of storage.
+ Valid literal values for the <quote>true</quote> state are:
+ <simplelist>
+ <member><literal>TRUE</literal></member>
+ <member><literal>'t'</literal></member>
+ <member><literal>'true'</literal></member>
+ <member><literal>'y'</literal></member>
+ <member><literal>'yes'</literal></member>
+ <member><literal>'1'</literal></member>
+ </simplelist>
+ For the <quote>false</quote> state, the following values can be
+ used:
+ <simplelist>
+ <member><literal>FALSE</literal></member>
+ <member><literal>'f'</literal></member>
+ <member><literal>'false'</literal></member>
+ <member><literal>'n'</literal></member>
+ <member><literal>'no'</literal></member>
+ <member><literal>'0'</literal></member>
+ </simplelist>
+ Using the key words <literal>TRUE</literal> and
+ <literal>FALSE</literal> is preferred (and
+ <acronym>SQL</acronym>-compliant).
</para>
+ <example id="datatype-boolean-example">
+ <title>Using the <type>boolean</type> type</title>
+
+<programlisting>
+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
+</programlisting>
+ </example>
+
<para>
- <table tocentry="1">
- <title><productname>Postgres</productname> Boolean Type</title>
- <titleabbrev>Booleans</titleabbrev>
- <tgroup cols="3">
- <thead>
- <row>
- <entry>State</entry>
- <entry>Input</entry>
- <entry>Output</entry>
- </row>
- </thead>
- <tbody>
- <row>
- <entry>True</entry>
- <entry>TRUE, 't', 'true', 'y', 'yes', '1'</entry>
- <entry><literal>t</literal></entry>
- </row>
- <row>
- <entry>False</entry>
- <entry>FALSE, 'f', 'false', 'n', 'no', '0'</entry>
- <entry><literal>f</literal></entry>
- </row>
- </tbody>
- </tgroup>
- </table>
+ <xref linkend="datatype-boolean-example"> shows that
+ <type>boolean</type> values are output using the letters
+ <literal>t</literal> and <literal>f</literal>.
+ </para>
+
+ <tip>
+ <para>
+ Values of the <type>boolean</type> type cannot be cast directly
+ to other types (e.g., <literal>CAST
+ (<replaceable>boolval</replaceable> AS integer)</literal> does
+ not work). This can be accomplished using the
+ <literal>CASE</literal> expression: <literal>CASE WHEN
+ <replaceable>boolval</replaceable> THEN 'value if true' ELSE
+ 'value if false' END</literal>. See also <xref
+ linkend="functions-conditional">.
+ </para>
+ </tip>
+
+ <para>
+ <type>boolean</type> uses 1 byte of storage.
</para>
</sect1>
<para>
<table tocentry="1">
- <title><productname>Postgres</productname> Geometric Types</title>
- <titleabbrev>Geometrics</titleabbrev>
+ <title>Geometric Types</title>
<tgroup cols="4">
<thead>
<row>
<term>(<replaceable>x2</replaceable>,<replaceable>y2</replaceable>)</term>
<listitem>
<para>
- The endpoints of the line segment.
+ The end points of the line segment.
</para>
</listitem>
</varlistentry>
<term>(<replaceable>x</replaceable>,<replaceable>y</replaceable>)</term>
<listitem>
<para>
- Endpoints of the line segments comprising the path.
+ 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.
</para>
<term>(<replaceable>x</replaceable>,<replaceable>y</replaceable>)</term>
<listitem>
<para>
- Endpoints of the line segments comprising the boundary of the
+ End points of the line segments comprising the boundary of the
polygon.
</para>
</listitem>
The <type>inet</type> 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,
+ network part of the address (the <quote>netmask</quote>). 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
<type>cidr</type> type rather than <type>inet</type>.
<replaceable>x</replaceable> specifies the maximum length.
<type>BIT</type> type data is automatically padded with 0's on the
right to the maximum length, <type>BIT VARYING</type> is of
- variable length. <type>BIT</type> without length is requivalent
+ variable length. <type>BIT</type> without length is equivalent
to <literal>BIT(1)</literal>, <type>BIT VARYING</type> means
unlimited length. Input data that is longer than the allowed
length will be truncated. Refer to <xref
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