REPOST: Re: Can joins be less efficient?

I'm sure there are times when any one method is better/or worse than any other method.

That is why EXPLAIN PLAN and TKPROF and DBMS_PROFILER, and GET_TIME exist: Use them.

But I do wonder if the person saying this to you is either lazy, from SQL Server/Sybase, or both?

Daniel Morgan

NoSpam wrote:

> I'm working on the code written by somebody else. What this code does is
> that it makes a query to the DB to obtain a resultset. Then from each row of
> the resultset, it repeatedly makes a second query to obtain a second
> resultset by using the key field in the first as a key to the second. It is
> very obvious that the two queries can be combined with a simple join. But
> this person insisted that there are times that cascaded reading of the
> resultsets can be faster than a simple join but he couldn't give me an
> example. I just wonder if it really can be true and under what circumstances
> that reading two resultsets can be faster than a single resultset with a
> join when a common key field exists in both tables.
>
> TIA

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