Selecting from joined tables (simple question)

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Subject: Selecting from joined tables (simple question)
Posted by:  willy_gat…@hotmail.com
Date: 29 Jan 2004

Thanks for help with this one

I have 2 tables

DATA_STANDARD with columns ID and VALUE

and

DATA_EXTRA with column DS_ID and EXTRA_VALUE

The idea is that extra information is stored in the DATA_EXTRA table
when required.

How do I select all values from DATA_STANDARD where there is either no
entry in DATA_EXTRA or EXTRA_VALUE is zero.

something like this?

select ds.id from DATA_STANDARD ds, DATA_EXTRA de
where
( ds.id not in ( select DS_ID from DATA_EXTRA ) )
or
(
  --Join
  ( ds.id = de.DS_ID )
  and
  ( de.extra_value is null )
)

Why is this wrong?

Thanks

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