Re: [SQL] Order by

At 17:49 +0300 on 02/06/1999, Jan Wieck wrote:


>     GROUP BY must be  possible  in  a  view's  query  expression.
>     Without  that  views  with aggregate columns could never work
>     properly.
>
>     If I now read your above statements right, "query expression"
>     ->  "query specification" -> "table expression" also forbid's
>     GROUP BY, because it cannot occur in  a  table  expression  -
>     right?  That  means  that  a  fully SQL92 compliant DB cannot
>     support aggregates in view definitions?

No, "table expression" includes "group by" and "having", because they
define the data itself. They actually say something about the set of
tuples. Here is the "table expression" definition:

   ::=              [  ]       [  ]       [  ]

Here is the "query specification":
   ::=       SELECT [  ]  
   ::=                |  [ {   }... ]
   ::=                |   
   ::=  [  ]
   ::= [ AS ] 

Finally, if you wondered where the syntax allows for unions and such like
for the definition of a view, here it is:
   ::=            | 
    ::=            |  UNION  [ ALL ] [  ] 
     |  EXCEPT [ ALL ] [  ] 

    ::=            | 
    ::=            |  INTERSECT [ ALL ] [  ] 

    ::=            | 
    ::=            |   
    ::=            |      | 
    ::= TABLE 
    ::=     CORRESPONDING [ BY    ]

    ::= 

Herouth

--
Herouth Maoz, Internet developer.
Open University of Israel - Telem project
http://telem.openu.ac.il/~herutma