Re: Oracle Decode Function

> would be interested to hear a valid reason why you feel the need> to use decode().

Just let me start by saying that this is NOT for me (see the original 
email in thread)! Personally, I have no trouble using CASE. However, if 
I want to create an Oracle-compatibilty layer, I have to implement all 
Oracle functions both good and bad ... my opinion either way is totally 
irrelevant!
> if you find yourself using the decode statement, you are probably> doing something wrong. why have it, do you _need_
it?

The only place I have found DECODE/CASE to be attractive is in ORDER BY 
clauses (hunts through code for example) ... imagine an LOV based on the 
following:

create table some_list (id integer, label varchar(20), position integer);

-- defaults
insert into some_list values (-1,'Any Value',0)
insert into some_list values (0,'No Value',0)
-- values
insert into some_list values (1,'Apple',2)
insert into some_list values (2,'Orange',1)

select id, name from some_list
order by decode(id,-1,-999,0,-998,position) asc

Of course this is a highly diluted example so don't over-analyze it but 
the intent is for the "default" entries (IDs -1 and 0) to always appear 
first while giving the user the ability to change the label and position 
values (but not the id) of any row, including the defaults. In this 
case, shy of restricting the input for position based on individual row 
IDs (imagine this is a JSP app), it makes much more sense to override 
the position column using the id column and then just use a function 
based index.
> seems that oracle gives you alot of functions and> abilities that allow dba's and programmers to be lazy, instead of>
havinga good db [relational] design (and that is more standards> compliant).
 

Oh heck yeah ... of course they do that! It locks you in to their 
platform and makes migrating apps off of Oracle a more expensive 
proposition. It's a really smart move when you have a huge chunk of the 
market and you want to keep it that way. That's why converting from 
PostgreSQL to Oracle is relatively easy while the reverse is ... well 
tough. Oracle used to encourage standards but now the only thing I see 
being encouraged is lock in ... that's why I'm here! ;-)

Chris Humphries wrote:
> if you find yourself using the decode statement, you are probably
> doing something wrong. why have it, do you _need_ it?
> 
> if you are using it for display strings based on conditions, 
> you shouldnt be using a function to do this. it should be a table,
> or something in the middle layer. try to keep the frame of mind of
> letting the db do it's job of just managing data; middle layer for
> doing something useful with the data and sending to the top layer
> for presentation or formatted data that is meaningful there. It 
> is the right(tm) way to do things, and will make life alot easier :)
> 
> would be interested to hear a valid reason why you feel the need
> to use decode(). seems that oracle gives you alot of functions and
> abilities that allow dba's and programmers to be lazy, instead of 
> having a good db [relational] design (and that is more standards
> compliant). 
> 
> though like Tom Lane said, there is case, if you need it. 
> good luck!
> 
> -chris
> 
> Marc Lavergne writes:
>  > That would get ugly in a real hurry! Oracle does get around the issue of 
>  > parameter datatypes by having automatic datatype conversions, more or 
>  > less, everything becomes a varchar2. The only real attractants to 
>  > implementing a DECODE() function is that it's one less thing to convert 
>  > when migrating apps from Oracle and, unfortunately, this is also a piece 
>  > of the SQL*Net compatibility that I'm looking into doing!
>  > 
>  > 
>  > Tom Lane wrote:
>  > > Marc Lavergne <mlavergne-pub@richlava.com> writes:
>  > > 
>  > >>If you're asking about whether a custom function can have vararg 
>  > >>parameters, the answer appears to depend on the CREATE FUNCTION
>  > >>syntax. 
>  > > 
>  > > 
>  > > Can't do it, though you could imagine creating a family of functions
>  > > of the same name and different numbers of parameters.  Trying to
>  > > emulate DECODE this way would have a much worse problem: what's the
>  > > datatype of the parameters?  (Or the result?)
>  > > 
>  > > Use CASE; it does more than DECODE *and* is ANSI-standard.
>  > > 
>  > >             regards, tom lane
>  > > 
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