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diff --git a/doc/src/sgml/html/datatype-datetime.html b/doc/src/sgml/html/datatype-datetime.html index 8a4534d..a70596d 100644 --- a/doc/src/sgml/html/datatype-datetime.html +++ b/doc/src/sgml/html/datatype-datetime.html @@ -1,5 +1,5 @@ <?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>8.5. Date/Time 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-binary.html" title="8.4. Binary Data Types" /><link rel="next" href="datatype-boolean.html" title="8.6. Boolean Type" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">8.5. Date/Time Types</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="datatype-binary.html" title="8.4. Binary 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 15.6 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="datatype-boolean.html" title="8.6. Boolean Type">Next</a></td></tr></table><hr /></div><div class="sect1" id="DATATYPE-DATETIME"><div class="titlepage"><div><div><h2 class="title" style="clear: both">8.5. Date/Time Types</h2></div></div></div><div class="toc"><dl class="toc"><dt><span class="sect2"><a href="datatype-datetime.html#DATATYPE-DATETIME-INPUT">8.5.1. Date/Time Input</a></span></dt><dt><span class="sect2"><a href="datatype-datetime.html#DATATYPE-DATETIME-OUTPUT">8.5.2. Date/Time Output</a></span></dt><dt><span class="sect2"><a href="datatype-datetime.html#DATATYPE-TIMEZONES">8.5.3. Time Zones</a></span></dt><dt><span class="sect2"><a href="datatype-datetime.html#DATATYPE-INTERVAL-INPUT">8.5.4. Interval Input</a></span></dt><dt><span class="sect2"><a href="datatype-datetime.html#DATATYPE-INTERVAL-OUTPUT">8.5.5. Interval Output</a></span></dt></dl></div><a id="id-1.5.7.13.2" class="indexterm"></a><a id="id-1.5.7.13.3" class="indexterm"></a><a id="id-1.5.7.13.4" class="indexterm"></a><a id="id-1.5.7.13.5" class="indexterm"></a><a id="id-1.5.7.13.6" class="indexterm"></a><a id="id-1.5.7.13.7" class="indexterm"></a><a id="id-1.5.7.13.8" class="indexterm"></a><a id="id-1.5.7.13.9" class="indexterm"></a><a id="id-1.5.7.13.10" class="indexterm"></a><a id="id-1.5.7.13.11" class="indexterm"></a><p> +<!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>8.5. Date/Time 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-binary.html" title="8.4. Binary Data Types" /><link rel="next" href="datatype-boolean.html" title="8.6. Boolean Type" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">8.5. Date/Time Types</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="datatype-binary.html" title="8.4. Binary 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 15.7 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="datatype-boolean.html" title="8.6. Boolean Type">Next</a></td></tr></table><hr /></div><div class="sect1" id="DATATYPE-DATETIME"><div class="titlepage"><div><div><h2 class="title" style="clear: both">8.5. Date/Time Types</h2></div></div></div><div class="toc"><dl class="toc"><dt><span class="sect2"><a href="datatype-datetime.html#DATATYPE-DATETIME-INPUT">8.5.1. Date/Time Input</a></span></dt><dt><span class="sect2"><a href="datatype-datetime.html#DATATYPE-DATETIME-OUTPUT">8.5.2. Date/Time Output</a></span></dt><dt><span class="sect2"><a href="datatype-datetime.html#DATATYPE-TIMEZONES">8.5.3. Time Zones</a></span></dt><dt><span class="sect2"><a href="datatype-datetime.html#DATATYPE-INTERVAL-INPUT">8.5.4. Interval Input</a></span></dt><dt><span class="sect2"><a href="datatype-datetime.html#DATATYPE-INTERVAL-OUTPUT">8.5.5. Interval Output</a></span></dt></dl></div><a id="id-1.5.7.13.2" class="indexterm"></a><a id="id-1.5.7.13.3" class="indexterm"></a><a id="id-1.5.7.13.4" class="indexterm"></a><a id="id-1.5.7.13.5" class="indexterm"></a><a id="id-1.5.7.13.6" class="indexterm"></a><a id="id-1.5.7.13.7" class="indexterm"></a><a id="id-1.5.7.13.8" class="indexterm"></a><a id="id-1.5.7.13.9" class="indexterm"></a><a id="id-1.5.7.13.10" class="indexterm"></a><a id="id-1.5.7.13.11" class="indexterm"></a><p> <span class="productname">PostgreSQL</span> supports the full set of <acronym class="acronym">SQL</acronym> date and time types, shown in <a class="xref" href="datatype-datetime.html#DATATYPE-DATETIME-TABLE" title="Table 8.9. Date/Time Types">Table 8.9</a>. The operations available on these data types are described in @@ -244,7 +244,7 @@ TIMESTAMP WITH TIME ZONE '2004-10-19 10:23:54+02' the date and time. <span class="productname">PostgreSQL</span> accepts that format on input, but on output it uses a space rather than <code class="literal">T</code>, as shown above. This is for readability and for consistency with - <a class="ulink" href="https://tools.ietf.org/html/rfc3339" target="_top">RFC 3339</a> as + <a class="ulink" href="https://datatracker.ietf.org/doc/html/rfc3339" target="_top">RFC 3339</a> as well as some other database systems. </p></div><p> In the <acronym class="acronym">SQL</acronym> and POSTGRES styles, day appears before @@ -479,10 +479,29 @@ P [<span class="optional"> <em class="replaceable"><code>years</code></em>-<em c used. To avoid ambiguity, it's recommended to attach an explicit sign to each field if any field is negative. </p><p> - Field values can have fractional parts: for example, <code class="literal">'1.5 + Internally, <code class="type">interval</code> values are stored as three integral + fields: months, days, and microseconds. These fields are kept + separate because the number of days in a month varies, while a day + can have 23 or 25 hours if a daylight savings time transition is + involved. An interval input string that uses other units is + normalized into this format, and then reconstructed in a standardized + way for output, for example: + +</p><pre class="programlisting"> +SELECT '2 years 15 months 100 weeks 99 hours 123456789 milliseconds'::interval; + interval +--------------------------------------- + 3 years 3 mons 700 days 133:17:36.789 +</pre><p> + + Here weeks, which are understood as <span class="quote">“<span class="quote">7 days</span>”</span>, have been + kept separate, while the smaller and larger time units were + combined and normalized. + </p><p> + Input field values can have fractional parts, for example <code class="literal">'1.5 weeks'</code> or <code class="literal">'01:02:03.45'</code>. However, - because interval internally stores only three integer units (months, - days, microseconds), fractional units must be spilled to smaller + because <code class="type">interval</code> internally stores only integral fields, + fractional values must be converted into smaller units. Fractional parts of units greater than months are rounded to be an integer number of months, e.g. <code class="literal">'1.5 years'</code> becomes <code class="literal">'1 year 6 mons'</code>. Fractional parts of @@ -494,32 +513,20 @@ P [<span class="optional"> <em class="replaceable"><code>years</code></em>-<em c </p><p> <a class="xref" href="datatype-datetime.html#DATATYPE-INTERVAL-INPUT-EXAMPLES" title="Table 8.17. Interval Input">Table 8.17</a> shows some examples of valid <code class="type">interval</code> input. - </p><div class="table" id="DATATYPE-INTERVAL-INPUT-EXAMPLES"><p class="title"><strong>Table 8.17. Interval Input</strong></p><div class="table-contents"><table class="table" summary="Interval Input" border="1"><colgroup><col /><col /></colgroup><thead><tr><th>Example</th><th>Description</th></tr></thead><tbody><tr><td><code class="literal">1-2</code></td><td>SQL standard format: 1 year 2 months</td></tr><tr><td><code class="literal">3 4:05:06</code></td><td>SQL standard format: 3 days 4 hours 5 minutes 6 seconds</td></tr><tr><td><code class="literal">1 year 2 months 3 days 4 hours 5 minutes 6 seconds</code></td><td>Traditional Postgres format: 1 year 2 months 3 days 4 hours 5 minutes 6 seconds</td></tr><tr><td><code class="literal">P1Y2M3DT4H5M6S</code></td><td>ISO 8601 <span class="quote">“<span class="quote">format with designators</span>”</span>: same meaning as above</td></tr><tr><td><code class="literal">P0001-02-03T04:05:06</code></td><td>ISO 8601 <span class="quote">“<span class="quote">alternative format</span>”</span>: same meaning as above</td></tr></tbody></table></div></div><br class="table-break" /><p> - Internally <code class="type">interval</code> values are stored as months, days, - and microseconds. This is done because the number of days in a month - varies, and a day can have 23 or 25 hours if a daylight savings - time adjustment is involved. The months and days fields are integers - while the microseconds field can store fractional seconds. Because intervals are - usually created from constant strings or <code class="type">timestamp</code> subtraction, - this storage method works well in most cases, but can cause unexpected - results: - -</p><pre class="programlisting"> -SELECT EXTRACT(hours from '80 minutes'::interval); - date_part ------------ - 1 - -SELECT EXTRACT(days from '80 hours'::interval); - date_part ------------ - 0 -</pre><p> - - Functions <code class="function">justify_days</code> and - <code class="function">justify_hours</code> are available for adjusting days - and hours that overflow their normal ranges. - </p></div><div class="sect2" id="DATATYPE-INTERVAL-OUTPUT"><div class="titlepage"><div><div><h3 class="title">8.5.5. Interval Output</h3></div></div></div><a id="id-1.5.7.13.22.2" class="indexterm"></a><p> + </p><div class="table" id="DATATYPE-INTERVAL-INPUT-EXAMPLES"><p class="title"><strong>Table 8.17. Interval Input</strong></p><div class="table-contents"><table class="table" summary="Interval Input" border="1"><colgroup><col /><col /></colgroup><thead><tr><th>Example</th><th>Description</th></tr></thead><tbody><tr><td><code class="literal">1-2</code></td><td>SQL standard format: 1 year 2 months</td></tr><tr><td><code class="literal">3 4:05:06</code></td><td>SQL standard format: 3 days 4 hours 5 minutes 6 seconds</td></tr><tr><td><code class="literal">1 year 2 months 3 days 4 hours 5 minutes 6 seconds</code></td><td>Traditional Postgres format: 1 year 2 months 3 days 4 hours 5 minutes 6 seconds</td></tr><tr><td><code class="literal">P1Y2M3DT4H5M6S</code></td><td>ISO 8601 <span class="quote">“<span class="quote">format with designators</span>”</span>: same meaning as above</td></tr><tr><td><code class="literal">P0001-02-03T04:05:06</code></td><td>ISO 8601 <span class="quote">“<span class="quote">alternative format</span>”</span>: same meaning as above</td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="DATATYPE-INTERVAL-OUTPUT"><div class="titlepage"><div><div><h3 class="title">8.5.5. Interval Output</h3></div></div></div><a id="id-1.5.7.13.22.2" class="indexterm"></a><p> + As previously explained, <span class="productname">PostgreSQL</span> + stores <code class="type">interval</code> values as months, days, and + microseconds. For output, the months field is converted to years and + months by dividing by 12. The days field is shown as-is. The + microseconds field is converted to hours, minutes, seconds, and + fractional seconds. Thus months, minutes, and seconds will never be + shown as exceeding the ranges 0–11, 0–59, and 0–59 + respectively, while the displayed years, days, and hours fields can + be quite large. (The <a class="link" href="functions-datetime.html#FUNCTION-JUSTIFY-DAYS"><code class="function">justify_days</code></a> + and <a class="link" href="functions-datetime.html#FUNCTION-JUSTIFY-HOURS"><code class="function">justify_hours</code></a> + functions can be used if it is desirable to transpose large days or + hours values into the next higher field.) + </p><p> The output format of the interval type can be set to one of the four styles <code class="literal">sql_standard</code>, <code class="literal">postgres</code>, <code class="literal">postgres_verbose</code>, or <code class="literal">iso_8601</code>, @@ -547,4 +554,4 @@ SELECT EXTRACT(days from '80 hours'::interval); The output of the <code class="literal">iso_8601</code> style matches the <span class="quote">“<span class="quote">format with designators</span>”</span> described in section 4.4.3.2 of the ISO 8601 standard. - </p><div class="table" id="INTERVAL-STYLE-OUTPUT-TABLE"><p class="title"><strong>Table 8.18. Interval Output Style Examples</strong></p><div class="table-contents"><table class="table" summary="Interval Output Style Examples" border="1"><colgroup><col /><col /><col /><col /></colgroup><thead><tr><th>Style Specification</th><th>Year-Month Interval</th><th>Day-Time Interval</th><th>Mixed Interval</th></tr></thead><tbody><tr><td><code class="literal">sql_standard</code></td><td>1-2</td><td>3 4:05:06</td><td>-1-2 +3 -4:05:06</td></tr><tr><td><code class="literal">postgres</code></td><td>1 year 2 mons</td><td>3 days 04:05:06</td><td>-1 year -2 mons +3 days -04:05:06</td></tr><tr><td><code class="literal">postgres_verbose</code></td><td>@ 1 year 2 mons</td><td>@ 3 days 4 hours 5 mins 6 secs</td><td>@ 1 year 2 mons -3 days 4 hours 5 mins 6 secs ago</td></tr><tr><td><code class="literal">iso_8601</code></td><td>P1Y2M</td><td>P3DT4H5M6S</td><td>P-1Y-2M3DT-4H-5M-6S</td></tr></tbody></table></div></div><br class="table-break" /></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="datatype-binary.html" title="8.4. Binary 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-boolean.html" title="8.6. Boolean Type">Next</a></td></tr><tr><td width="40%" align="left" valign="top">8.4. Binary Data Types </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 15.6 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 8.6. Boolean Type</td></tr></table></div></body></html>
\ No newline at end of file + </p><div class="table" id="INTERVAL-STYLE-OUTPUT-TABLE"><p class="title"><strong>Table 8.18. Interval Output Style Examples</strong></p><div class="table-contents"><table class="table" summary="Interval Output Style Examples" border="1"><colgroup><col /><col /><col /><col /></colgroup><thead><tr><th>Style Specification</th><th>Year-Month Interval</th><th>Day-Time Interval</th><th>Mixed Interval</th></tr></thead><tbody><tr><td><code class="literal">sql_standard</code></td><td>1-2</td><td>3 4:05:06</td><td>-1-2 +3 -4:05:06</td></tr><tr><td><code class="literal">postgres</code></td><td>1 year 2 mons</td><td>3 days 04:05:06</td><td>-1 year -2 mons +3 days -04:05:06</td></tr><tr><td><code class="literal">postgres_verbose</code></td><td>@ 1 year 2 mons</td><td>@ 3 days 4 hours 5 mins 6 secs</td><td>@ 1 year 2 mons -3 days 4 hours 5 mins 6 secs ago</td></tr><tr><td><code class="literal">iso_8601</code></td><td>P1Y2M</td><td>P3DT4H5M6S</td><td>P-1Y-2M3DT-4H-5M-6S</td></tr></tbody></table></div></div><br class="table-break" /></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="datatype-binary.html" title="8.4. Binary 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-boolean.html" title="8.6. Boolean Type">Next</a></td></tr><tr><td width="40%" align="left" valign="top">8.4. Binary Data Types </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 15.7 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 8.6. Boolean Type</td></tr></table></div></body></html>
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