Where Clause in Parenthesis

[Darren Reely]

Joe Boyle wrote:
> first of all I would suggest that you place the 'where' clause in brackets
> as below. 

>         where  ( (im.credit_note_flag   =  'Y'  ) and &
>                 (id.gl_account_no      <> 'D2480'   )   )


Joe,

Is that one of those 'Old School' practices again. Based on the WHERE 
clause above, parenthesis seem to simply be a setup for possible 
confusion with no added value.

I suppose the reason to add extra parenthesis could be due to knowledge 
of a particular database engine. Years ago when I worked with the 
Digital RDB database, via Pascal, we had an expert tell us that 
parenthesis helped the RDB engine make more efficient queries. And sure 
enough, we saw some performance gains by carefully rearranging our 
statements within grouped parenthesis.

Darren