Full Select Statement explanation

*   adapted from Sunderraman, "Oracle Programming: A Primer", section 2.4.7, 
pp. 53-54

*   <sub-select> general form:

        select	[distinct] <expression> {, <expression>}
        from	<tablename> [<alias>]{, <tablename> [<alias>]}
        [where	<search_condition>]
        [group by	<column> {, <column>}]
        [having	<condition>]

*   <select> general form:

        <sub-select>
        {union [all] | intersect | minus <sub-select>}
        [order by	result_column [asc|desc] {, result_column [asc|desc]}

*   note that order by clause must come at the end of a select, and since 
it really only affects "output", it cannot be in a sub-select;

*   important: CONCEPTUAL order of evaluation (may not ACTUALLY be what 
SQL uses, because of efficiency/optimization, but you can think of it 
this way) (Sunderraman pp. 53-54)
        (1)   The product of all tables in the from clause [of the 
	"outer"/initial sub-select] is formed.
        (2)   The where clause [of the "outer"/initial sub-select]  is 
	evaluated to eliminate rows that do not 
        satisfy the search_condition.
        (3)   The rows are grouped using the columns in the group by 
	clause [of the "outer"/initial sub-select].
        (4)   Groups that do not satisfy the condition in the having 
	clause [of the "outer"/initial sub-select]  
        are eliminated.
        (5)   The expressions in the select clause target list [of the 
	"outer"/initial sub-select]  are evaluated.
        (6)   If the distinct keyword is present in the select clause [of 
	the "outer"/initial sub-select], duplicate 
        rows are now eliminated.
        (7)   The union/intersect/minus is taken after each sub-select is 
	evaluated.
        (8)   The resulting rows are sorted according to the columns 
	specified in the order by clause.

*   <sub-select> general form:         

                (6)         (5)
      select	[distinct]  <expression> {, <expression>}
(1)   from	<tablename> [<alias>]{, <tablename> [<alias>]} 
(2)   [where	<search_condition>]
(3)   [group by	<column> {, <column>}]
(4)   [having	<condition>]

*   <select> general form:

      <sub-select>
(7)   {union [all] | intersect | minus <sub-select>}
(8)   [order by	result_column [asc|desc] {, result_column [asc|desc]}

*   (and, of course, for each sub-select "connected" by union or 
intersect or minus, and for each sub-select buried within a 
search-condition, you'd do steps (1)-(6) above.)