FUNCTION crosstab_float8_5_cols(
    IN text,
    OUT my_row_name text,
    OUT my_category_1 float8,
    OUT my_category_2 float8,
    OUT my_category_3 float8,
    OUT my_category_4 float8,
    OUT my_category_5 float8)
  RETURNS setof record
  AS '$libdir/tablefunc','crosstab' LANGUAGE C STABLE STRICT;
</programlisting>
      </para>
     </listitem>
    </itemizedlist>
    </para>

  </sect3>

  <sect3 id="tablefunc-functions-crosstab-text-2">
   <title><function>crosstab(text, text)</function></title>

   <indexterm>
    <primary>crosstab</primary>
   </indexterm>

<synopsis>
crosstab(text source_sql, text category_sql)
</synopsis>

   <para>
    The main limitation of the single-parameter form of <function>crosstab</function>
    is that it treats all values in a group alike, inserting each value into
    the first available column.  If you want the value
    columns to correspond to specific categories of data, and some groups
    might not have data for some of the categories, that doesn't work well.
    The two-parameter form of <function>crosstab</function> handles this case by
    providing an explicit list of the categories corresponding to the
    output columns.
   </para>

   <para>
    <parameter>source_sql</parameter> is an SQL statement that produces the
    source set of data.  This statement must return one
    <structfield>row_name</structfield> column, one
    <structfield>category</structfield> column, and one
    <structfield>value</structfield> column. It may also have one or more
    <quote>extra</quote> columns.
    The <structfield>row_name</structfield> column must be first. The
    <structfield>category</structfield> and <structfield>value</structfield>
    columns must be the last two columns, in that order.  Any columns between
    <structfield>row_name</structfield> and
    <structfield>category</structfield> are treated as <quote>extra</quote>.
    The <quote>extra</quote> columns are expected to be the same for all rows
    with the same <structfield>row_name</structfield> value.
   </para>

   <para>
    For example, <parameter>source_sql</parameter> might produce a set
    something like:
<programlisting>
SELECT row_name, extra_col, cat, value FROM foo ORDER BY 1;

 row_name    extra_col   cat    value
----------+------------+-----+---------
  row1         extra1    cat1    val1
  row1         extra1    cat2    val2
  row1         extra1    cat4    val4
  row2         extra2    cat1    val5
  row2         extra2    cat2    val6
  row2         extra2    cat3    val7
  row2         extra2    cat4    val8
</programlisting>
   </para>

   <para>
    <parameter>category_sql</parameter> is an SQL statement that produces
    the set of categories. This statement must return only one column.
    It must produce at least one row, or an error will be generated.
    Also, it must not produce duplicate values, or an error will be
    generated.  <parameter>category_sql</parameter> might be something like:

<programlisting>
SELECT DISTINCT cat FROM foo ORDER BY 1;
    cat
  -------
    cat1
    cat2
    cat3
    cat4
</programlisting>
   </para>

   <para>
    The <function>crosstab</function> function is declared to return <type>setof
    record</type>, so the actual names and types of the output columns must be
    defined in the <literal>FROM</literal> clause of the calling <command>SELECT</command>
    statement, for example:

<programlisting>
SELECT * FROM crosstab('...', '...')
    AS ct(row_name text, extra text, cat1 text, cat2 text, cat3 text, cat4 text);
</programlisting>
   </para>

   <para>
    This will produce a result something like:
<programlisting>
                  &lt;==  value  columns   ==&gt;
row_name   extra   cat1   cat2   cat3   cat4
---------+-------+------+------+------+------
  row1     extra1  val1   val2          val4
  row2     extra2  val5   val6   val7   val8
</programlisting>
   </para>

   <para>
    The <literal>FROM</literal> clause must define the proper number of