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CONVERT ORACLE SQL TO EQUIVALENT ACCESS SQL ( using Oracle "dual" table )

Posted on 2004-09-09
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Last Modified: 2008-01-16
Hi All - wonder if anyone can help me with this ?

I am trying to convert an Oracle query in to an Access 2000 query.

I'm struggling with the following.

Within the FROM statement (of the oracle query) there is a subquery which looks like this ;

  (select table1.field1, table1.field2 from table1_long_name table1, table2_long_name table2
where table1.cor_id = table2.id and table2.reference in ('name1','name2','name3','name4')
   union select 'MISSING NUMBER', 'MISSING NUMBER' from dual)

what would the equivalent Acess SQL be ?

Don't really understand this whole 'dual' caper at all ?  

thank you,

dan
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Question by:Dan_Wong
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9 Comments
 
LVL 41

Expert Comment

by:shanesuebsahakarn
ID: 12017609
"dual" looks to be a table name. The equvalent Access/Jet subquery would be identical to the SQL that you have posted above, if that is the case. It could be re-written using INNER JOINs but that would be generally unecessary.
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by:peter57r
peter57r earned 200 total points
ID: 12017631
Hello Dan_Wong,

I think to make this work you just need to set up a table called Dual which contains 1 record of 1 field (any datatype but a number field defaulting to 1 would protect against duplicates).
I don't think there is any change needed to the SQL.

Pete
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LVL 41

Expert Comment

by:shanesuebsahakarn
ID: 12017678
It actually wouldn't matter how many records the "Dual" table contains (although only one record would be faster) - since the UNION clause includes an implied DISTINCT statement.
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by:Dan_Wong
ID: 12017808
So what does this subquery do ?

i.e. what 's the purpose of -

union select 'MISSING NUMBER', 'MISSING NUMBER' from dual

?

d.
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by:GRayL
GRayL earned 200 total points
ID: 12017939
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Accepted Solution

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shanesuebsahakarn earned 1600 total points
ID: 12017986
The UNION SELECT blah blah is basically adding a single record to the subquery with two fields, both of which contain the word "MISSING NUMBER". It's a common technique that is often used in Access to add something like "(all records)" as an option in a combo box, for example.
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by:Dan_Wong
ID: 12018083
Hmm o.k. i think that I understand that vaguely...

In which case if I create a table in Access called 'Dual' with a single record.

This should have an identical effect as whatever the original statement intended ?

d.
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Expert Comment

by:shanesuebsahakarn
ID: 12018143
Yes, that's right.
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by:Dan_Wong
ID: 12018164
o.k.

Thanks All.



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