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How to delete a record using SQL

Posted on 2004-08-12
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Last Modified: 2010-04-05
Hi, I have a question

I have two tables A and B. I want to delete a record in A and all the record with the same ArtikelID in B. How can i do this by using SQL ?
Can You answer ASAP

thx
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Question by:marioway
5 Comments
 
LVL 12

Expert Comment

by:Ivanov_G
ID: 11783956
DELETE
FROM A
WHERE A.ID IN (SELECT B.ID FROM B)
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Expert Comment

by:Ivanov_G
ID: 11784030
Now I red carefully your question... My query delete only records from A that have records with the same ID in B.

You will need to use stored procedure to achieve what you want.
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Expert Comment

by:mokule
ID: 11784039
From my appliation


      sid := DM1.atSubst.FieldByName('sub_id').AsInteger;
      DM1.ADOConnection1.BeginTrans;
      try
        DM1.ADOCommand1.CommandText :=
          Format('DELETE FROM SubstNames WHERE nam_subst_id=%d', [sid]);
        DM1.ADOCommand1.Execute;

        DM1.ADOCommand1.CommandText :=
          Format('DELETE FROM Substances WHERE sub_id=%d',[sid]);
        DM1.ADOCommand1.Execute;

        DM1.ADOConnection1.CommitTrans;
      except
        DM1.ADOConnection1.RollbackTrans;
        end;
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Accepted Solution

by:
Wim ten Brink earned 500 total points
ID: 11785175
You need to execute two queries.

DELETE from B where ArtikelID = :ArtikelID;
DELETE from A where ArtikelID = :ArtikelID;

I've given parameterized queries here as example. Now, it could be possible that ADO can work with multi-query commands so you could put this in a single ADOQuery component. But in general it's better to put both queries in their own ADOQuery components.

Now, some databases can maintain relationships between tables for you and offer the option of cascading deletes. This means that if you delete a record from table A, all related records from B (and C, D, E and F) will be deleted too. But again, this depends upon how the database is set up. (How you created it!)

I'm not that good as a database expert so someone might help you with that. But cascading deletes might be useful for you...
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Author Comment

by:marioway
ID: 11792883
Thx
a lot

Marioway
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