Re: [GENERAL] Except operation

[Adriaan Joubert]

Satyajeet Seth wrote:
> 
> Hi
> The query:
> select * from webdata except select * from webdata1;
>  takes abysmally long .How can I optimise it?
> The particulars are:

You could try 

  select * from webdata w
  where not exists 
        (select * from webdata1 w1
         where w1.tid=w.tid
          ...
        )

If you have the correct indexes on webdata1 this can be quite fast.

Adriaan

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