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paull
Yak Posting Veteran
50 Posts |
 Posted - 2009-11-24 : 09:28:48
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| Hi guys!I cant see what I am doing wrong here!!I have a query that picks up data from 5 tables and merges it into one "Final" table.. basically Insert into Final (URN, VAR1, VA2...)select d.URN, d.VAR1, m.VAR2, v.VAR3 etc etc)from data d, model m, verbs vwhere d.URN = m.URN etc etc plus I only want certain ID that are stored in another table Keeps kso "and k.URN=d.URN.This has worked fine in the past but now I am getting a lot of duplicates in the Final table. Can anyone see where I am might be going wrong (its driving me mad!) and, would it be better / more efficient to use a sub query (you'll have to excuse me as I am still learning!) something like "in (select URN from Keeps)" Please correct me if I'm wrong!Many many thanks |
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webfred
Master Smack Fu Yak Hacker
8781 Posts |
Posted - 2009-11-24 : 10:09:20
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1.) We cannot see your "real" select statement, so it is not easy to say what happens.2.) Run that select without the insert-part and have a look at the joined data. Often there is the reason of dups.3.) Have a look at your destination table - maybe some records are already there...4.) Don't join like that from table1, table2, ... better use from table1 join table2 on ...
No, you're never too old to Yak'n'Roll if you're too young to die. |
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paull
Yak Posting Veteran
50 Posts |
Posted - 2009-11-24 : 10:16:31
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| Hi WebfredThanks for the tip of running it without the Insert - I found where the dupes are coming from!!Is there a reason not to join as I have, speed, accuracy etc, this query has developed and evolved since I started learning SQL so I am keen to update it where I should and use better code- I find it a good way to learn!! |
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webfred
Master Smack Fu Yak Hacker
8781 Posts |
Posted - 2009-11-24 : 10:32:32
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Using the "JOIN-Syntax" is much better readable.You can see the join conditions direct in relation to the joined tables.Joining by table1, table2, ... will be deprecated somewhere in the future...
No, you're never too old to Yak'n'Roll if you're too young to die. |
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