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diff --git a/doc/src/sgml/html/datatype-numeric.html b/doc/src/sgml/html/datatype-numeric.html new file mode 100644 index 0000000..e8df3c1 --- /dev/null +++ b/doc/src/sgml/html/datatype-numeric.html @@ -0,0 +1,370 @@ +<?xml version="1.0" encoding="UTF-8" standalone="no"?> +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>8.1. Numeric Types</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="datatype.html" title="Chapter 8. Data Types" /><link rel="next" href="datatype-money.html" title="8.2. Monetary Types" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">8.1. Numeric Types</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="datatype.html" title="Chapter 8. Data Types">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="datatype.html" title="Chapter 8. Data Types">Up</a></td><th width="60%" align="center">Chapter 8. Data Types</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 15.5 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="datatype-money.html" title="8.2. Monetary Types">Next</a></td></tr></table><hr /></div><div class="sect1" id="DATATYPE-NUMERIC"><div class="titlepage"><div><div><h2 class="title" style="clear: both">8.1. Numeric Types</h2></div></div></div><div class="toc"><dl class="toc"><dt><span class="sect2"><a href="datatype-numeric.html#DATATYPE-INT">8.1.1. Integer Types</a></span></dt><dt><span class="sect2"><a href="datatype-numeric.html#DATATYPE-NUMERIC-DECIMAL">8.1.2. Arbitrary Precision Numbers</a></span></dt><dt><span class="sect2"><a href="datatype-numeric.html#DATATYPE-FLOAT">8.1.3. Floating-Point Types</a></span></dt><dt><span class="sect2"><a href="datatype-numeric.html#DATATYPE-SERIAL">8.1.4. Serial Types</a></span></dt></dl></div><a id="id-1.5.7.9.2" class="indexterm"></a><p> + Numeric types consist of two-, four-, and eight-byte integers, + four- and eight-byte floating-point numbers, and selectable-precision + decimals. <a class="xref" href="datatype-numeric.html#DATATYPE-NUMERIC-TABLE" title="Table 8.2. Numeric Types">Table 8.2</a> lists the + available types. + </p><div class="table" id="DATATYPE-NUMERIC-TABLE"><p class="title"><strong>Table 8.2. Numeric Types</strong></p><div class="table-contents"><table class="table" summary="Numeric Types" border="1"><colgroup><col class="col1" /><col class="col2" /><col class="col3" /><col class="col4" /></colgroup><thead><tr><th>Name</th><th>Storage Size</th><th>Description</th><th>Range</th></tr></thead><tbody><tr><td><code class="type">smallint</code></td><td>2 bytes</td><td>small-range integer</td><td>-32768 to +32767</td></tr><tr><td><code class="type">integer</code></td><td>4 bytes</td><td>typical choice for integer</td><td>-2147483648 to +2147483647</td></tr><tr><td><code class="type">bigint</code></td><td>8 bytes</td><td>large-range integer</td><td>-9223372036854775808 to +9223372036854775807</td></tr><tr><td><code class="type">decimal</code></td><td>variable</td><td>user-specified precision, exact</td><td>up to 131072 digits before the decimal point; up to 16383 digits after the decimal point</td></tr><tr><td><code class="type">numeric</code></td><td>variable</td><td>user-specified precision, exact</td><td>up to 131072 digits before the decimal point; up to 16383 digits after the decimal point</td></tr><tr><td><code class="type">real</code></td><td>4 bytes</td><td>variable-precision, inexact</td><td>6 decimal digits precision</td></tr><tr><td><code class="type">double precision</code></td><td>8 bytes</td><td>variable-precision, inexact</td><td>15 decimal digits precision</td></tr><tr><td><code class="type">smallserial</code></td><td>2 bytes</td><td>small autoincrementing integer</td><td>1 to 32767</td></tr><tr><td><code class="type">serial</code></td><td>4 bytes</td><td>autoincrementing integer</td><td>1 to 2147483647</td></tr><tr><td><code class="type">bigserial</code></td><td>8 bytes</td><td>large autoincrementing integer</td><td>1 to 9223372036854775807</td></tr></tbody></table></div></div><br class="table-break" /><p> + The syntax of constants for the numeric types is described in + <a class="xref" href="sql-syntax-lexical.html#SQL-SYNTAX-CONSTANTS" title="4.1.2. Constants">Section 4.1.2</a>. The numeric types have a + full set of corresponding arithmetic operators and + functions. Refer to <a class="xref" href="functions.html" title="Chapter 9. Functions and Operators">Chapter 9</a> for more + information. The following sections describe the types in detail. + </p><div class="sect2" id="DATATYPE-INT"><div class="titlepage"><div><div><h3 class="title">8.1.1. Integer Types</h3></div></div></div><a id="id-1.5.7.9.6.2" class="indexterm"></a><a id="id-1.5.7.9.6.3" class="indexterm"></a><a id="id-1.5.7.9.6.4" class="indexterm"></a><a id="id-1.5.7.9.6.5" class="indexterm"></a><a id="id-1.5.7.9.6.6" class="indexterm"></a><a id="id-1.5.7.9.6.7" class="indexterm"></a><p> + The types <code class="type">smallint</code>, <code class="type">integer</code>, and + <code class="type">bigint</code> store whole numbers, that is, numbers without + fractional components, of various ranges. Attempts to store + values outside of the allowed range will result in an error. + </p><p> + The type <code class="type">integer</code> is the common choice, as it offers + the best balance between range, storage size, and performance. + The <code class="type">smallint</code> type is generally only used if disk + space is at a premium. The <code class="type">bigint</code> type is designed to be + used when the range of the <code class="type">integer</code> type is insufficient. + </p><p> + <acronym class="acronym">SQL</acronym> only specifies the integer types + <code class="type">integer</code> (or <code class="type">int</code>), + <code class="type">smallint</code>, and <code class="type">bigint</code>. The + type names <code class="type">int2</code>, <code class="type">int4</code>, and + <code class="type">int8</code> are extensions, which are also used by some + other <acronym class="acronym">SQL</acronym> database systems. + </p></div><div class="sect2" id="DATATYPE-NUMERIC-DECIMAL"><div class="titlepage"><div><div><h3 class="title">8.1.2. Arbitrary Precision Numbers</h3></div></div></div><a id="id-1.5.7.9.7.2" class="indexterm"></a><a id="id-1.5.7.9.7.3" class="indexterm"></a><a id="id-1.5.7.9.7.4" class="indexterm"></a><p> + The type <code class="type">numeric</code> can store numbers with a + very large number of digits. It is especially recommended for + storing monetary amounts and other quantities where exactness is + required. Calculations with <code class="type">numeric</code> values yield exact + results where possible, e.g., addition, subtraction, multiplication. + However, calculations on <code class="type">numeric</code> values are very slow + compared to the integer types, or to the floating-point types + described in the next section. + </p><p> + We use the following terms below: The + <em class="firstterm">precision</em> of a <code class="type">numeric</code> + is the total count of significant digits in the whole number, + that is, the number of digits to both sides of the decimal point. + The <em class="firstterm">scale</em> of a <code class="type">numeric</code> is the + count of decimal digits in the fractional part, to the right of the + decimal point. So the number 23.5141 has a precision of 6 and a + scale of 4. Integers can be considered to have a scale of zero. + </p><p> + Both the maximum precision and the maximum scale of a + <code class="type">numeric</code> column can be + configured. To declare a column of type <code class="type">numeric</code> use + the syntax: +</p><pre class="programlisting"> +NUMERIC(<em class="replaceable"><code>precision</code></em>, <em class="replaceable"><code>scale</code></em>) +</pre><p> + The precision must be positive, while the scale may be positive or + negative (see below). Alternatively: +</p><pre class="programlisting"> +NUMERIC(<em class="replaceable"><code>precision</code></em>) +</pre><p> + selects a scale of 0. Specifying: +</p><pre class="programlisting"> +NUMERIC +</pre><p> + without any precision or scale creates an <span class="quote">“<span class="quote">unconstrained + numeric</span>”</span> column in which numeric values of any length can be + stored, up to the implementation limits. A column of this kind will + not coerce input values to any particular scale, whereas + <code class="type">numeric</code> columns with a declared scale will coerce + input values to that scale. (The <acronym class="acronym">SQL</acronym> standard + requires a default scale of 0, i.e., coercion to integer + precision. We find this a bit useless. If you're concerned + about portability, always specify the precision and scale + explicitly.) + </p><div class="note"><h3 class="title">Note</h3><p> + The maximum precision that can be explicitly specified in + a <code class="type">numeric</code> type declaration is 1000. An + unconstrained <code class="type">numeric</code> column is subject to the limits + described in <a class="xref" href="datatype-numeric.html#DATATYPE-NUMERIC-TABLE" title="Table 8.2. Numeric Types">Table 8.2</a>. + </p></div><p> + If the scale of a value to be stored is greater than the declared + scale of the column, the system will round the value to the specified + number of fractional digits. Then, if the number of digits to the + left of the decimal point exceeds the declared precision minus the + declared scale, an error is raised. + For example, a column declared as +</p><pre class="programlisting"> +NUMERIC(3, 1) +</pre><p> + will round values to 1 decimal place and can store values between + -99.9 and 99.9, inclusive. + </p><p> + Beginning in <span class="productname">PostgreSQL</span> 15, it is allowed + to declare a <code class="type">numeric</code> column with a negative scale. Then + values will be rounded to the left of the decimal point. The + precision still represents the maximum number of non-rounded digits. + Thus, a column declared as +</p><pre class="programlisting"> +NUMERIC(2, -3) +</pre><p> + will round values to the nearest thousand and can store values + between -99000 and 99000, inclusive. + It is also allowed to declare a scale larger than the declared + precision. Such a column can only hold fractional values, and it + requires the number of zero digits just to the right of the decimal + point to be at least the declared scale minus the declared precision. + For example, a column declared as +</p><pre class="programlisting"> +NUMERIC(3, 5) +</pre><p> + will round values to 5 decimal places and can store values between + -0.00999 and 0.00999, inclusive. + </p><div class="note"><h3 class="title">Note</h3><p> + <span class="productname">PostgreSQL</span> permits the scale in a + <code class="type">numeric</code> type declaration to be any value in the range + -1000 to 1000. However, the <acronym class="acronym">SQL</acronym> standard requires + the scale to be in the range 0 to <em class="replaceable"><code>precision</code></em>. + Using scales outside that range may not be portable to other database + systems. + </p></div><p> + Numeric values are physically stored without any extra leading or + trailing zeroes. Thus, the declared precision and scale of a column + are maximums, not fixed allocations. (In this sense the <code class="type">numeric</code> + type is more akin to <code class="type">varchar(<em class="replaceable"><code>n</code></em>)</code> + than to <code class="type">char(<em class="replaceable"><code>n</code></em>)</code>.) The actual storage + requirement is two bytes for each group of four decimal digits, + plus three to eight bytes overhead. + </p><a id="id-1.5.7.9.7.13" class="indexterm"></a><a id="id-1.5.7.9.7.14" class="indexterm"></a><a id="id-1.5.7.9.7.15" class="indexterm"></a><p> + In addition to ordinary numeric values, the <code class="type">numeric</code> type + has several special values: +</p><div class="literallayout"><p><br /> +<code class="literal">Infinity</code><br /> +<code class="literal">-Infinity</code><br /> +<code class="literal">NaN</code><br /> +</p></div><p> + These are adapted from the IEEE 754 standard, and represent + <span class="quote">“<span class="quote">infinity</span>”</span>, <span class="quote">“<span class="quote">negative infinity</span>”</span>, and + <span class="quote">“<span class="quote">not-a-number</span>”</span>, respectively. When writing these values + as constants in an SQL command, you must put quotes around them, + for example <code class="literal">UPDATE table SET x = '-Infinity'</code>. + On input, these strings are recognized in a case-insensitive manner. + The infinity values can alternatively be spelled <code class="literal">inf</code> + and <code class="literal">-inf</code>. + </p><p> + The infinity values behave as per mathematical expectations. For + example, <code class="literal">Infinity</code> plus any finite value equals + <code class="literal">Infinity</code>, as does <code class="literal">Infinity</code> + plus <code class="literal">Infinity</code>; but <code class="literal">Infinity</code> + minus <code class="literal">Infinity</code> yields <code class="literal">NaN</code> (not a + number), because it has no well-defined interpretation. Note that an + infinity can only be stored in an unconstrained <code class="type">numeric</code> + column, because it notionally exceeds any finite precision limit. + </p><p> + The <code class="literal">NaN</code> (not a number) value is used to represent + undefined calculational results. In general, any operation with + a <code class="literal">NaN</code> input yields another <code class="literal">NaN</code>. + The only exception is when the operation's other inputs are such that + the same output would be obtained if the <code class="literal">NaN</code> were to + be replaced by any finite or infinite numeric value; then, that output + value is used for <code class="literal">NaN</code> too. (An example of this + principle is that <code class="literal">NaN</code> raised to the zero power + yields one.) + </p><div class="note"><h3 class="title">Note</h3><p> + In most implementations of the <span class="quote">“<span class="quote">not-a-number</span>”</span> concept, + <code class="literal">NaN</code> is not considered equal to any other numeric + value (including <code class="literal">NaN</code>). In order to allow + <code class="type">numeric</code> values to be sorted and used in tree-based + indexes, <span class="productname">PostgreSQL</span> treats <code class="literal">NaN</code> + values as equal, and greater than all non-<code class="literal">NaN</code> + values. + </p></div><p> + The types <code class="type">decimal</code> and <code class="type">numeric</code> are + equivalent. Both types are part of the <acronym class="acronym">SQL</acronym> + standard. + </p><p> + When rounding values, the <code class="type">numeric</code> type rounds ties away + from zero, while (on most machines) the <code class="type">real</code> + and <code class="type">double precision</code> types round ties to the nearest even + number. For example: + +</p><pre class="programlisting"> +SELECT x, + round(x::numeric) AS num_round, + round(x::double precision) AS dbl_round +FROM generate_series(-3.5, 3.5, 1) as x; + x | num_round | dbl_round +------+-----------+----------- + -3.5 | -4 | -4 + -2.5 | -3 | -2 + -1.5 | -2 | -2 + -0.5 | -1 | -0 + 0.5 | 1 | 0 + 1.5 | 2 | 2 + 2.5 | 3 | 2 + 3.5 | 4 | 4 +(8 rows) +</pre><p> + </p></div><div class="sect2" id="DATATYPE-FLOAT"><div class="titlepage"><div><div><h3 class="title">8.1.3. Floating-Point Types</h3></div></div></div><a id="id-1.5.7.9.8.2" class="indexterm"></a><a id="id-1.5.7.9.8.3" class="indexterm"></a><a id="id-1.5.7.9.8.4" class="indexterm"></a><a id="id-1.5.7.9.8.5" class="indexterm"></a><a id="id-1.5.7.9.8.6" class="indexterm"></a><p> + The data types <code class="type">real</code> and <code class="type">double precision</code> are + inexact, variable-precision numeric types. On all currently supported + platforms, these types are implementations of <acronym class="acronym">IEEE</acronym> + Standard 754 for Binary Floating-Point Arithmetic (single and double + precision, respectively), to the extent that the underlying processor, + operating system, and compiler support it. + </p><p> + Inexact means that some values cannot be converted exactly to the + internal format and are stored as approximations, so that storing + and retrieving a value might show slight discrepancies. + Managing these errors and how they propagate through calculations + is the subject of an entire branch of mathematics and computer + science and will not be discussed here, except for the + following points: + </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p> + If you require exact storage and calculations (such as for + monetary amounts), use the <code class="type">numeric</code> type instead. + </p></li><li class="listitem"><p> + If you want to do complicated calculations with these types + for anything important, especially if you rely on certain + behavior in boundary cases (infinity, underflow), you should + evaluate the implementation carefully. + </p></li><li class="listitem"><p> + Comparing two floating-point values for equality might not + always work as expected. + </p></li></ul></div><p> + </p><p> + On all currently supported platforms, the <code class="type">real</code> type has a + range of around 1E-37 to 1E+37 with a precision of at least 6 decimal + digits. The <code class="type">double precision</code> type has a range of around + 1E-307 to 1E+308 with a precision of at least 15 digits. Values that are + too large or too small will cause an error. Rounding might take place if + the precision of an input number is too high. Numbers too close to zero + that are not representable as distinct from zero will cause an underflow + error. + </p><p> + By default, floating point values are output in text form in their + shortest precise decimal representation; the decimal value produced is + closer to the true stored binary value than to any other value + representable in the same binary precision. (However, the output value is + currently never <span class="emphasis"><em>exactly</em></span> midway between two + representable values, in order to avoid a widespread bug where input + routines do not properly respect the round-to-nearest-even rule.) This value will + use at most 17 significant decimal digits for <code class="type">float8</code> + values, and at most 9 digits for <code class="type">float4</code> values. + </p><div class="note"><h3 class="title">Note</h3><p> + This shortest-precise output format is much faster to generate than the + historical rounded format. + </p></div><p> + For compatibility with output generated by older versions + of <span class="productname">PostgreSQL</span>, and to allow the output + precision to be reduced, the <a class="xref" href="runtime-config-client.html#GUC-EXTRA-FLOAT-DIGITS">extra_float_digits</a> + parameter can be used to select rounded decimal output instead. Setting a + value of 0 restores the previous default of rounding the value to 6 + (for <code class="type">float4</code>) or 15 (for <code class="type">float8</code>) + significant decimal digits. Setting a negative value reduces the number + of digits further; for example -2 would round output to 4 or 13 digits + respectively. + </p><p> + Any value of <a class="xref" href="runtime-config-client.html#GUC-EXTRA-FLOAT-DIGITS">extra_float_digits</a> greater than 0 + selects the shortest-precise format. + </p><div class="note"><h3 class="title">Note</h3><p> + Applications that wanted precise values have historically had to set + <a class="xref" href="runtime-config-client.html#GUC-EXTRA-FLOAT-DIGITS">extra_float_digits</a> to 3 to obtain them. For + maximum compatibility between versions, they should continue to do so. + </p></div><a id="id-1.5.7.9.8.15" class="indexterm"></a><a id="id-1.5.7.9.8.16" class="indexterm"></a><p> + In addition to ordinary numeric values, the floating-point types + have several special values: +</p><div class="literallayout"><p><br /> +<code class="literal">Infinity</code><br /> +<code class="literal">-Infinity</code><br /> +<code class="literal">NaN</code><br /> +</p></div><p> + These represent the IEEE 754 special values + <span class="quote">“<span class="quote">infinity</span>”</span>, <span class="quote">“<span class="quote">negative infinity</span>”</span>, and + <span class="quote">“<span class="quote">not-a-number</span>”</span>, respectively. When writing these values + as constants in an SQL command, you must put quotes around them, + for example <code class="literal">UPDATE table SET x = '-Infinity'</code>. On input, + these strings are recognized in a case-insensitive manner. + The infinity values can alternatively be spelled <code class="literal">inf</code> + and <code class="literal">-inf</code>. + </p><div class="note"><h3 class="title">Note</h3><p> + IEEE 754 specifies that <code class="literal">NaN</code> should not compare equal + to any other floating-point value (including <code class="literal">NaN</code>). + In order to allow floating-point values to be sorted and used + in tree-based indexes, <span class="productname">PostgreSQL</span> treats + <code class="literal">NaN</code> values as equal, and greater than all + non-<code class="literal">NaN</code> values. + </p></div><p> + <span class="productname">PostgreSQL</span> also supports the SQL-standard + notations <code class="type">float</code> and + <code class="type">float(<em class="replaceable"><code>p</code></em>)</code> for specifying + inexact numeric types. Here, <em class="replaceable"><code>p</code></em> specifies + the minimum acceptable precision in <span class="emphasis"><em>binary</em></span> digits. + <span class="productname">PostgreSQL</span> accepts + <code class="type">float(1)</code> to <code class="type">float(24)</code> as selecting the + <code class="type">real</code> type, while + <code class="type">float(25)</code> to <code class="type">float(53)</code> select + <code class="type">double precision</code>. Values of <em class="replaceable"><code>p</code></em> + outside the allowed range draw an error. + <code class="type">float</code> with no precision specified is taken to mean + <code class="type">double precision</code>. + </p></div><div class="sect2" id="DATATYPE-SERIAL"><div class="titlepage"><div><div><h3 class="title">8.1.4. Serial Types</h3></div></div></div><a id="id-1.5.7.9.9.2" class="indexterm"></a><a id="id-1.5.7.9.9.3" class="indexterm"></a><a id="id-1.5.7.9.9.4" class="indexterm"></a><a id="id-1.5.7.9.9.5" class="indexterm"></a><a id="id-1.5.7.9.9.6" class="indexterm"></a><a id="id-1.5.7.9.9.7" class="indexterm"></a><a id="id-1.5.7.9.9.8" class="indexterm"></a><a id="id-1.5.7.9.9.9" class="indexterm"></a><div class="note"><h3 class="title">Note</h3><p> + This section describes a PostgreSQL-specific way to create an + autoincrementing column. Another way is to use the SQL-standard + identity column feature, described at <a class="xref" href="sql-createtable.html" title="CREATE TABLE"><span class="refentrytitle">CREATE TABLE</span></a>. + </p></div><p> + The data types <code class="type">smallserial</code>, <code class="type">serial</code> and + <code class="type">bigserial</code> are not true types, but merely + a notational convenience for creating unique identifier columns + (similar to the <code class="literal">AUTO_INCREMENT</code> property + supported by some other databases). In the current + implementation, specifying: + +</p><pre class="programlisting"> +CREATE TABLE <em class="replaceable"><code>tablename</code></em> ( + <em class="replaceable"><code>colname</code></em> SERIAL +); +</pre><p> + + is equivalent to specifying: + +</p><pre class="programlisting"> +CREATE SEQUENCE <em class="replaceable"><code>tablename</code></em>_<em class="replaceable"><code>colname</code></em>_seq AS integer; +CREATE TABLE <em class="replaceable"><code>tablename</code></em> ( + <em class="replaceable"><code>colname</code></em> integer NOT NULL DEFAULT nextval('<em class="replaceable"><code>tablename</code></em>_<em class="replaceable"><code>colname</code></em>_seq') +); +ALTER SEQUENCE <em class="replaceable"><code>tablename</code></em>_<em class="replaceable"><code>colname</code></em>_seq OWNED BY <em class="replaceable"><code>tablename</code></em>.<em class="replaceable"><code>colname</code></em>; +</pre><p> + + Thus, we have created an integer column and arranged for its default + values to be assigned from a sequence generator. A <code class="literal">NOT NULL</code> + constraint is applied to ensure that a null value cannot be + inserted. (In most cases you would also want to attach a + <code class="literal">UNIQUE</code> or <code class="literal">PRIMARY KEY</code> constraint to prevent + duplicate values from being inserted by accident, but this is + not automatic.) Lastly, the sequence is marked as <span class="quote">“<span class="quote">owned by</span>”</span> + the column, so that it will be dropped if the column or table is dropped. + </p><div class="note"><h3 class="title">Note</h3><p> + Because <code class="type">smallserial</code>, <code class="type">serial</code> and + <code class="type">bigserial</code> are implemented using sequences, there may + be "holes" or gaps in the sequence of values which appears in the + column, even if no rows are ever deleted. A value allocated + from the sequence is still "used up" even if a row containing that + value is never successfully inserted into the table column. This + may happen, for example, if the inserting transaction rolls back. + See <code class="literal">nextval()</code> in <a class="xref" href="functions-sequence.html" title="9.17. Sequence Manipulation Functions">Section 9.17</a> + for details. + </p></div><p> + To insert the next value of the sequence into the <code class="type">serial</code> + column, specify that the <code class="type">serial</code> + column should be assigned its default value. This can be done + either by excluding the column from the list of columns in + the <code class="command">INSERT</code> statement, or through the use of + the <code class="literal">DEFAULT</code> key word. + </p><p> + The type names <code class="type">serial</code> and <code class="type">serial4</code> are + equivalent: both create <code class="type">integer</code> columns. The type + names <code class="type">bigserial</code> and <code class="type">serial8</code> work + the same way, except that they create a <code class="type">bigint</code> + column. <code class="type">bigserial</code> should be used if you anticipate + the use of more than 2<sup>31</sup> identifiers over the + lifetime of the table. The type names <code class="type">smallserial</code> and + <code class="type">serial2</code> also work the same way, except that they + create a <code class="type">smallint</code> column. + </p><p> + The sequence created for a <code class="type">serial</code> column is + automatically dropped when the owning column is dropped. + You can drop the sequence without dropping the column, but this + will force removal of the column default expression. + </p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="datatype.html" title="Chapter 8. Data Types">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="datatype.html" title="Chapter 8. Data Types">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="datatype-money.html" title="8.2. Monetary Types">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 8. Data Types </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 15.5 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 8.2. Monetary Types</td></tr></table></div></body></html>
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