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diff --git a/doc/src/sgml/html/dml-returning.html b/doc/src/sgml/html/dml-returning.html new file mode 100644 index 0000000..7bb12b2 --- /dev/null +++ b/doc/src/sgml/html/dml-returning.html @@ -0,0 +1,53 @@ +<?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>6.4. Returning Data from Modified Rows</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="dml-delete.html" title="6.3. Deleting Data" /><link rel="next" href="queries.html" title="Chapter 7. Queries" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">6.4. Returning Data from Modified Rows</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="dml-delete.html" title="6.3. Deleting Data">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="dml.html" title="Chapter 6. Data Manipulation">Up</a></td><th width="60%" align="center">Chapter 6. Data Manipulation</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="queries.html" title="Chapter 7. Queries">Next</a></td></tr></table><hr /></div><div class="sect1" id="DML-RETURNING"><div class="titlepage"><div><div><h2 class="title" style="clear: both">6.4. Returning Data from Modified Rows</h2></div></div></div><a id="id-1.5.5.6.2" class="indexterm"></a><a id="id-1.5.5.6.3" class="indexterm"></a><a id="id-1.5.5.6.4" class="indexterm"></a><a id="id-1.5.5.6.5" class="indexterm"></a><p> + Sometimes it is useful to obtain data from modified rows while they are + being manipulated. The <code class="command">INSERT</code>, <code class="command">UPDATE</code>, + and <code class="command">DELETE</code> commands all have an + optional <code class="literal">RETURNING</code> clause that supports this. Use + of <code class="literal">RETURNING</code> avoids performing an extra database query to + collect the data, and is especially valuable when it would otherwise be + difficult to identify the modified rows reliably. + </p><p> + The allowed contents of a <code class="literal">RETURNING</code> clause are the same as + a <code class="command">SELECT</code> command's output list + (see <a class="xref" href="queries-select-lists.html" title="7.3. Select Lists">Section 7.3</a>). It can contain column + names of the command's target table, or value expressions using those + columns. A common shorthand is <code class="literal">RETURNING *</code>, which selects + all columns of the target table in order. + </p><p> + In an <code class="command">INSERT</code>, the data available to <code class="literal">RETURNING</code> is + the row as it was inserted. This is not so useful in trivial inserts, + since it would just repeat the data provided by the client. But it can + be very handy when relying on computed default values. For example, + when using a <a class="link" href="datatype-numeric.html#DATATYPE-SERIAL" title="8.1.4. Serial Types"><code class="type">serial</code></a> + column to provide unique identifiers, <code class="literal">RETURNING</code> can return + the ID assigned to a new row: +</p><pre class="programlisting"> +CREATE TABLE users (firstname text, lastname text, id serial primary key); + +INSERT INTO users (firstname, lastname) VALUES ('Joe', 'Cool') RETURNING id; +</pre><p> + The <code class="literal">RETURNING</code> clause is also very useful + with <code class="literal">INSERT ... SELECT</code>. + </p><p> + In an <code class="command">UPDATE</code>, the data available to <code class="literal">RETURNING</code> is + the new content of the modified row. For example: +</p><pre class="programlisting"> +UPDATE products SET price = price * 1.10 + WHERE price <= 99.99 + RETURNING name, price AS new_price; +</pre><p> + </p><p> + In a <code class="command">DELETE</code>, the data available to <code class="literal">RETURNING</code> is + the content of the deleted row. For example: +</p><pre class="programlisting"> +DELETE FROM products + WHERE obsoletion_date = 'today' + RETURNING *; +</pre><p> + </p><p> + If there are triggers (<a class="xref" href="triggers.html" title="Chapter 39. Triggers">Chapter 39</a>) on the target table, + the data available to <code class="literal">RETURNING</code> is the row as modified by + the triggers. Thus, inspecting columns computed by triggers is another + common use-case for <code class="literal">RETURNING</code>. + </p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="dml-delete.html" title="6.3. Deleting Data">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="dml.html" title="Chapter 6. Data Manipulation">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="queries.html" title="Chapter 7. Queries">Next</a></td></tr><tr><td width="40%" align="left" valign="top">6.3. Deleting Data </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"> Chapter 7. Queries</td></tr></table></div></body></html>
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