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>6.4. Returning Data From Modified Rows</A
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><P
>   Sometimes it is useful to obtain data from modified rows while they are
   being manipulated.  The <TT
CLASS="COMMAND"
>INSERT</TT
>, <TT
CLASS="COMMAND"
>UPDATE</TT
>,
   and <TT
CLASS="COMMAND"
>DELETE</TT
> commands all have an
   optional <TT
CLASS="LITERAL"
>RETURNING</TT
> clause that supports this.  Use
   of <TT
CLASS="LITERAL"
>RETURNING</TT
> 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 <TT
CLASS="LITERAL"
>RETURNING</TT
> clause are the same as
   a <TT
CLASS="COMMAND"
>SELECT</TT
> command's output list
   (see <A
HREF="queries-select-lists.html"
>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 <TT
CLASS="LITERAL"
>RETURNING *</TT
>, which selects
   all columns of the target table in order.
  </P
><P
>   In an <TT
CLASS="COMMAND"
>INSERT</TT
>, the data available to <TT
CLASS="LITERAL"
>RETURNING</TT
> 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
HREF="datatype-numeric.html#DATATYPE-SERIAL"
><TT
CLASS="TYPE"
>serial</TT
></A
>
   column to provide unique identifiers, <TT
CLASS="LITERAL"
>RETURNING</TT
> 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 <TT
CLASS="LITERAL"
>RETURNING</TT
> clause is also very useful
   with <TT
CLASS="LITERAL"
>INSERT ... SELECT</TT
>.
  </P
><P
>   In an <TT
CLASS="COMMAND"
>UPDATE</TT
>, the data available to <TT
CLASS="LITERAL"
>RETURNING</TT
> is
   the new content of the modified row.  For example:
</P><PRE
CLASS="PROGRAMLISTING"
>UPDATE products SET price = price * 1.10
  WHERE price &lt;= 99.99
  RETURNING name, price AS new_price;</PRE
><P>
  </P
><P
>   In a <TT
CLASS="COMMAND"
>DELETE</TT
>, the data available to <TT
CLASS="LITERAL"
>RETURNING</TT
> 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
HREF="triggers.html"
>Chapter 37</A
>) on the target table,
   the data available to <TT
CLASS="LITERAL"
>RETURNING</TT
> is the row as modified by
   the triggers.  Thus, inspecting columns computed by triggers is another
   common use-case for <TT
CLASS="LITERAL"
>RETURNING</TT
>.
  </P
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