Re: Why use it : SELECT 1 FROM DUAL
From: Tim Gorman <tim_at_evdbt.com>
Date: Thu, 02 Aug 2012 12:00:53 -0600
Message-ID: <501AC055.5060202_at_evdbt.com>
Lots of developers, when generating SQL statements dynamically, use the predicate "1 = 1" or something similar so as not to leave an "AND" keyword dangling without a predicate. So, for example they'll have an IF-THEN-ELSE condition in the code building the SQL statement that generates an actual predicate in the THEN condition and hard-codes the no-op of "1 = 1" in the ELSE condition.
Date: Thu, 02 Aug 2012 12:00:53 -0600
Message-ID: <501AC055.5060202_at_evdbt.com>
Lots of developers, when generating SQL statements dynamically, use the predicate "1 = 1" or something similar so as not to leave an "AND" keyword dangling without a predicate. So, for example they'll have an IF-THEN-ELSE condition in the code building the SQL statement that generates an actual predicate in the THEN condition and hard-codes the no-op of "1 = 1" in the ELSE condition.
It's an artifact of a slightly clumsy programming method, rather than any form of optimization.
On 8/2/2012 11:52 AM, Eriovaldo Andrietta wrote:
> Hello friends,
> I am analyzing some sql statments and found out in all queries the
> developer added the following where clause plus others...
>
> and exists (select 1 from dual)
>
>
> All queries has this code.
>
> Is there any good reason to put it in the sql statment ?
> Does it improve performance ?
>
> This is the first time I see it in SQL ?
>
> Regards
> Eriovaldo
-- http://www.freelists.org/webpage/oracle-lReceived on Thu Aug 02 2012 - 13:00:53 CDT