Oracle FAQ Your Portal to the Oracle Knowledge Grid
HOME | ASK QUESTION | ADD INFO | SEARCH | E-MAIL US
 

Home -> Community -> Usenet -> comp.databases.theory -> Re: Simple SQL?

Re: Simple SQL?

From: JRStern <JRStern_at_gte.net>
Date: Mon, 21 May 2001 19:18:49 GMT
Message-ID: <3b0969fa.4960843@news.gte.net>

On Sun, 20 May 2001 15:02:20 -0700, "Isaac Blank" <izblank_at_yahoo.com> wrote:
> The keyword is, of course, "multiple", right? Well, if there are
>multiple tables or table expressions mentioned in the FROM clause, then it
>is a join. In our case both FROM clauses you underlined only mention one
>table each, so they are not joins, but subqueries that happen to be
>correlated - because the WHERE clause contains references to the outer query
>context.

Piffle. Lots of antique SQL has multitable equates in the FROM clause, even when values are only selected from one table. Your assertion is that these are EXISTS and not JOINS. Well, then, use the EXIST syntax in the query, and I'll grant you style points. However, under the covers, the engine still has to look at two tables, and it's going to be a rare system today that does this simple kind of query much differently, no matter what syntax you use.

So, as you speculate, I tend to be lazy and use join syntax rather than Exists, but I'd prefer either to the simple equate in the From.

J. Received on Mon May 21 2001 - 14:18:49 CDT

Original text of this message

HOME | ASK QUESTION | ADD INFO | SEARCH | E-MAIL US