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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>.
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