'smith'), ('bob', 'jones'), ('joe', 'blow'))
     AS names(first, last)
</programlisting>
     Again, a table alias is optional.  Assigning alias names to the columns
     of the <command>VALUES</command> list is optional, but is good practice.
     For more information see <xref linkend="queries-values"/>.
    </para>

    <para>
     According to the SQL standard, a table alias name must be supplied
     for a subquery.  <productname>PostgreSQL</productname>
     allows <literal>AS</literal> and the alias to be omitted, but
     writing one is good practice in SQL code that might be ported to
     another system.
    </para>
   </sect3>

   <sect3 id="queries-tablefunctions">
    <title>Table Functions</title>

    <indexterm zone="queries-tablefunctions"><primary>table function</primary></indexterm>

    <indexterm zone="queries-tablefunctions">
     <primary>function</primary>
     <secondary>in the FROM clause</secondary>
    </indexterm>

    <para>
     Table functions are functions that produce a set of rows, made up
     of either base data types (scalar types) or composite data types
     (table rows).  They are used like a table, view, or subquery in
     the <literal>FROM</literal> clause of a query. Columns returned by table
     functions can be included in <literal>SELECT</literal>,
     <literal>JOIN</literal>, or <literal>WHERE</literal> clauses in the same manner
     as columns of a table, view, or subquery.
    </para>

    <para>
     Table functions may also be combined using the <literal>ROWS FROM</literal>
     syntax, with the results returned in parallel columns; the number of
     result rows in this case is that of the largest function result, with
     smaller results padded with null values to match.
    </para>

<synopsis>
<replaceable>function_call</replaceable> <optional>WITH ORDINALITY</optional> <optional><optional>AS</optional> <replaceable>table_alias</replaceable> <optional>(<replaceable>column_alias</replaceable> <optional>, ... </optional>)</optional></optional>
ROWS FROM( <replaceable>function_call</replaceable> <optional>, ... </optional> ) <optional>WITH ORDINALITY</optional> <optional><optional>AS</optional> <replaceable>table_alias</replaceable> <optional>(<replaceable>column_alias</replaceable> <optional>, ... </optional>)</optional></optional>
</synopsis>

    <para>
     If the <literal>WITH ORDINALITY</literal> clause is specified, an
     additional column of type <type>bigint</type> will be added to the
     function result columns.  This column numbers the rows of the function
     result set, starting from 1. (This is a generalization of the
     SQL-standard syntax for <literal>UNNEST ... WITH ORDINALITY</literal>.)
     By default, the ordinal column is called <literal>ordinality</literal>, but
     a different column name can be assigned to it using
     an <literal>AS</literal> clause.
    </para>

    <para>
     The special table function <literal>UNNEST</literal> may be called with
     any number of array parameters, and it returns a corresponding number of
     columns, as if <literal>UNNEST</literal>
     (<xref linkend="functions-array"/>) had been called on each parameter
     separately and combined using the <literal>ROWS FROM</literal> construct.
    </para>

<synopsis>
UNNEST( <replaceable>array_expression</replaceable> <optional>, ... </optional> ) <optional>WITH ORDINALITY</optional> <optional><optional>AS</optional> <replaceable>table_alias</replaceable> <optional>(<replaceable>column_alias</replaceable> <optional>, ... </optional>)</optional></optional>
</synopsis>

    <para>
     If no <replaceable>table_alias</replaceable> is specified, the function
     name is used as the table name; in the case of a <literal>ROWS FROM()</literal>
     construct, the first function's name is used.
    </para>

    <para>
     If column aliases are not supplied, then for a function returning a base
     data type, the column name is also the same as the function name.