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(integer value 0 or real value 0.0) are excluded from the dataset before
continuing.)^

<p><b>3. Generation of the set of result rows.</b>
<tcl>hd_fragment resultset</tcl>
<tcl>hd_keywords {result-set expressions} {GROUP BY}</tcl>

<p>Once the input data from the FROM clause has been filtered by the
WHERE clause expression (if any), the set of result rows for the simple 
SELECT are calculated. Exactly how this is done depends on whether the simple 
SELECT is an aggregate or non-aggregate query, and whether or not a GROUP
BY clause was specified.


<p> The list of expressions between the SELECT and FROM keywords is known as
the result expression list.  ^If a result expression is the special expression


"*" then all columns in the input data are substituted for that one expression.
^(If the expression is the alias of a table or subquery in the FROM clause


followed by ".*" then all columns from the named table or subquery are
substituted for the single expression.)^ ^(It is an error to use a "*" or
"alias.*" expression in any context other than than a result expression list.)^
^(It is also an error to use a "*" or "alias.*" expression in a simple SELECT
query that does not have a FROM clause.)^

<p> ^(The number of columns in the rows returned by a simple SELECT statement
is equal to the number of expressions in the result expression list after
substitution of * and alias.* expressions.)^ Each result row is calculated by
evaluating the expressions in the result expression list with respect to a
single row of input data or, for aggregate queries, with respect to a group
of rows.

<ul>
  <li><p>^If the SELECT statement is <b>a non-aggregate query</b>, then 
    each expression in the result expression list is evaluated for each row in
    the dataset filtered by the WHERE clause.

  <li><p>^If the SELECT statement is <b>an aggregate query without a GROUP
    BY</b> clause, then each aggregate expression in the result-set is 
    evaluated once across the entire dataset. ^Each non-aggregate expression
    in the result-set is evaluated once for an arbitrarily selected row of
    the dataset. ^The same arbitrarily selected row is used for each
    non-aggregate expression. ^Or, if the dataset contains zero rows, then 
    each non-aggregate expression is evaluated against a row consisting
    entirely of NULL values.

   <p>^The single row of result-set data created by evaluating the aggregate
    and non-aggregate expressions in the result-set forms the result of an
    aggregate query without a GROUP BY clause. ^An aggregate query without a
    GROUP BY clause always returns exactly one row of data.

  <li><p>^If the SELECT statement is <b>an aggregate query with a GROUP