Re: Why use it : SELECT 1 FROM DUAL

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
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